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FIRST LINES

PHYSIOLOGY,

BEING AN

INTRODUCTION TO THE SCIENCE OF LIFE ;

WRITTEN IN POPULAR LANGUAGE.

DESIGNED FOR THE USE OF

COffllON SCHOOLS, ACADEMIES, AND GENEEAL READERS.

BY REYNELL COAXES, M.D.

AUTHOR OF THE FIRST LINES OF NATURAL PHILOSOPHy.-

SIXTH EDITION, REVISED;

WITH AN APPENDIX

PHILADELPHIA:
PUBLISHED BY E. H. BUTLER & CO.

1846.

—^°"'— '''--•■ - -

V--

Entered according to Act of Congress, in the 3'e:ir 1845, by Reyneix
CoATEs, M. D., in llie Clerk's Office of the District Court for the Eastern
Diistrict of Pennsylvania.

£ ftr^

J. FAGAN, STEREGTYPER.

(2)

TO
A. CRITTENTEN, ESQ.

PRINCIPAL OP THE ALBANY FEMALE ACADEMY.

In just admiration of the talent which conducts
to such noble results, the system of instruction
under his immediate superintendence — as proved
by both the mental culture and the manners of
his pupils,

THIS VOLUME
l^ft aac»j)ectfiill2 JBetricatetr,

BY THE AUTHOR.

(3)

PREFACE.

To the earlier editions of this little work, several pages
of prefatory matter appeared requisite, in order, partly, to
apologize for the introduction of a new candidate for popu-
lar favour, in a department of science for which several
introductory text-books adapted to the use of schools and
unprofessional readers had been previously produced, and,
partly, to defend the fitness of Physiology as a branch of
elementary education, not only for male children, but for
females also.

This necessity is no longer obvious. The rapid succes-
sion of reprints which the work has undergone furnishes
abundant evidence that it is calculated to supply a deficiency
in our means of instruction which is felt and acknowledged
by the public ; and the author has received, from t]\e pub-
lishers, the gratifying assurance that an ample share of the
patronage bestowed upon it has been derived from the fe-
male schools and academies of the country. He has, there-
fore, been induced to apply to more useful purpose the chief
part of the space formerly devoted to the preface; and now,
after very careful revision, the addition of a glossary, and a
slight change of title, he no longer fears the charge of im-
modest presumption in presenting the volume to teachers
and general readers who have not as yet examined its con-
tents, as a treatise that has been tested and approved upon
authority less questionable than his own.

Many essays designed for similar purposes are ushered
into the world with lofty pretensions as to the perfect man-
ner in which the whole field of Physiology is covered within
their pages. This pretension is an insult to the understand-
ing of the reader; and in the present undertaking, the au-
thor pretends to nothing more than the presentation of such

1 * (5)

VI PREFACE.

a general view of the science as he conceives to form a le-
gitimate portion of a strictly elementary education — such a
view as will enable the pupil, in after life, to comprehend
and to enjoy those profounder works on natural history,
hygiene, the fine arts, and even morals, which, without some
knowledge of Physiology, are either altogether unintelligi-
ble, or vaguely understood.

The practical teacher will find the references to the mat-
ter, whether in the Contents, the body of the work, the
Questions, or the Glossary, arranged according to the num-
bers of the paragraphs, and not those of the pages. The
Questions have been placed at the end of the text, rather
than the bottom of each page, with the express intention of
testing more perfectly the comprehension of the pupil ; and
they are so worded as to render almost impossible the in-
dulgence of the parrot-like propensity to answer in the pre-
cise words of the writer. The Glossary follows the Ques-
tions, and concludes the volume. It will be found interesting
to those who are fond of impressing technicalities upon the
memory by the aid of associations connected with their
derivation, and will prove a useful guide to the correct pro-
nunciation, as well as the true meaning of the few profes-
sional terms which have been unavoidably employed.

The character of the volume being that of a regular trea-
tise, and not a mere compilation, it will be reasonably ex-
pected that opinions peculiar to the writer may occasionally
appear. This introduction of novelty, so far as the predi-
cates are concerned, has been studiously avoided; but, in
the chain of the argument, conclusions strictly logical, and
therefore indisputable, have not been suppressed, mert^ly
because they have not been embalmed in the dust of the
library.

CONTENTS.

CHAPTER I.

OiN THE iMOTION AND GROWTH OF ANIMATE AND INANIMATE THINGS.

Paragraph
What constitutes the difFerence between things which have life

and things which have not, 1

Motion is not a proof of life, nor is its absence a proof of the

absence of life, 2

Illustrations. — The sleeping- dog — the moving watch 2

The stillness of the trees in the absence of wind — the

seeming vitality of the eye-stone, 3

Growth is not a proof of life, 4, 5

Illustrations. — The confused ideas of children on this subject
— growth of spars in caves — of saltpetre, mould, and mosses

in damp places — of iron ore in swamps, 8

Folly of supposing that rocks and stones have an inherent power

of growth, 9

Motion and growth are insufficient to distinguish animate from

inanimate things, 10

Birth and death are not inherent properties of living things, .... 11

Inanimate things cannot move by their own energy, but must be

moved by other things, 13

Illustrations. — Motion of a falling stone — a vibrating spring

— the eye-stone, 13

Living things are moved by other things ; but have also other

powers of motion, 14

Illustrations. — A man falling by gravity — the limb of a tree

vibrating when bent, 14

Inherent power of motion in living things, 15

Illustrations. — Motions of a potatoe sprouting in the dark, 15
Motions of leaves and flowers towards the light — motions

observed in DionoBa muscipula, 16

Motions of animals determined by will, 17

First distincth'e property of living things — the power of regulating

their own motions, 18

Explanation of the word organ, 19

of the term organized beings, 20

of the term organization, , 20

Division of matter into organic and inorganic matter, 22

Xll CONTENTS.

Paragraph
Explanation of the terms petrifaction and organic remains — 23

of the terra system, 24, 25

Difference in the mode of growth of animate and inanimate

things, 26

Inanimate things grow by additions to tlieir exterior, 27

liiving things grow by additions to their interior, 28, 29

Illustrations. — Tlie formation of sap and blood, 30

Living things construct their own particles, 31

Organized beings possess the power of moving their own fluids, 32
Apparent growth of inanimate things by internal additions ex-
plained, 33

Illustrations. — Experiment of a sponge in water,. . . ■ 33

Experiment of a hyacinth growing in water, 34

Experiment of iron swelled by heat, 35

Independent powers of motion in living things, 36

Our ignorance of the nature of life, 37

CHAPTER XL

ON THE INDIVIDUALITY OF ORGANIZED BEINGS, AND THE DIFFUSION OF
LIFE IN LIVING BODIES.

Peculiar powers of life enjoyed by every organ, 38

Explanation of the terms function and vital functions, 39

The mutual dependence of parts and their functions, • . . 40

The various degrees of importance of different organs, 41

The power of healing injuries is inversely as the complexity of

the organization, 42, 43

Illustrations. — Life in the amputated tail of a snake, the hind
legs of frogs, and the heads of turtles — life in tortoises

without brain or heart, and in the disembowelled shark,. . 45

Diffusion of vital power in simple animals, 46

Organization of animal and vegetable fluids — explanation of the

term assimilation, 47

Tiie nutritive fluids are possessed of life, 48

The simplicity of the fluids corresponds with the simplicity of

the solid structure of organized beings, 49-51

Illustration. — History of a medusa, 52-55

Independent life of pieces cut from animals of very simple organi-
zation, 56

History of the hydra viridis — the type of simphcity in animal

organization, 57

Digestion in the hydra, 58

Absorption in the hydra, •. 59

The great cavity of the hydra answ^ers the double purpose of

a stomach and a heart, 60

The hydra, when inverted, continues to live, 61

Multiplication of the hydra by artificial division, 62

Spontaneous division of the hydra, 63

CONTENTS. Xlll

Paragraph

Limits of the divisibility of the hydra, 64

Uniformity of structure in the hydra, 65

Explanation of the terms cellular membrane and cellular tissue, . 66, 67

Structure of cellular tissue, 68

Illustrations. — Inflation of fowls for market, 69

Effects of a fractured rib wounding the lungs, 70

Structure of fat — explanation of the term adipose tissue,. 71

Vital functions of the hydra, 72-77

Animals distinguished from vegetables by consciousness and

vfilL 78

CHAPTER III.

ON THE ORGANIZATION AND FUNCTIONS OF SIMPLE ANIMALS, APPARENTLY
DIVESTED OF SPECIAL ORGANS.

Minuteness of simple beings necessary to the preservation of the

race, 79

Simple beings — why confined to fluids, 80

Fixedness of many simple animals — their means of taking prey —

tentacula?, 81

Means of taking food — cilia, 82

Cilia and tentaculae of flustra carbacea, 83

Cilia are sometimes organs of locomotion — vorticella cyathina, . . 84

Contractility — motion of cilia not muscular, 85

Motion of cilia in respiration of larger animals, 86

Cilia in plants — chara hispida, 87

Gemmules — gemmules of flustra, 88

Polypi commonly live in families and have a common life, 89

Necessity for mechanical support in simple animals, 90

Several forms of calcareous or horny support, 91

Madrepore — effects on navigation, 94

Secretion — as seen in polypi, cuticle, shells, &c., 96

of lime and horn common to all animals and, probably,

to parts of animals, 98

Nutrition a kind of secretion, 99

Secretions sometimes act as motive powers — bile, 100

Functions of organic and animal life, 101

Contractility moves the fluids, 103

differs from inorganic contraction, which is the

result of cohesive attraction, 104

instances of — visible in plants and as displayed in

physalia megalista, 105

mode of taking prey in physalia, and its mode of

locomotion, 106

not necessarily dependent on will, 110

must be excited by some agent, 112 ,

Contraction results from the action of stimulants, 113

Tonicity, 114

diminished or destroyed by paralysis, fainting and sleep, 116

XIV CONTENTS.

Paragrapli

Tonicity — influenced by heat and cold, 117

of skin, 118

Various forms of tonicity — are they all due to the same cause?. 119

CHAPTER IV.

ON THE NECESSITY FOR A MASTICATORY AND DIGESTIVE APPARATUS IN
COMPLEX ANIMALS.

Simplicity of the elementary stomach, 121

Necessary division of the stomach in the medusa, 122

The ramifications of the stomach in medusa seem to supply the

place of blood-vessels, 123

Necessity for greater complexity as we ascend the scale — masti-

catory apparatus, 124

Early appearance of teeth and jaws — teeth and jaws in echinoder-

mata and in insects, 125

Internal masticatory organs, 126

Alimentary canal, 127

Gizzards, 128

Digestive apparatus — more simple in carnivorous animals, 130

of shell-fish complex, 131

simple in birds of prey, and complex in

beasts that live on vegetables, 132

CHAPTER V.

ON THE NECESSITY FOR A SPECIAL APPARATUS OF MOTION. THE MUSCULAR
AND OSSEOUS SYSTEMS AND THEIR APPENDAGES.

Necessity of a muscular system, ] 33

Muscular system, 134

Muscles of voluntary motion, 135

Necessity and existence of involuntary muscles, ] 36

Muscles of organic and animal life, 137

Mixed muscles, 138

Fascia, 139

Fascial system, 140

Uses of fasciae, 141

Structure of fascia, 142

Appearance of muscles — they are identical with flesh, 143

Arrangement of separate muscles, 144

Structure and colour of muscles, 146

Muscular fibre — structure of, 148

Cellular nidus of muscles, 149

Muscles between fragments of bone reduced to cellular tissue, . . 150

Attachments of muscles, 151

Cutaneous and fascial attachments of muscles, 151

Testaceous attachments, 152

CONTENTS. XV

Paragraph

Attachments in echinoderrnata, 153

Attachments in insects and Crustacea, 155

External skeletons and appendages of the skin, 156

Necessity for an internal skeleton in more complex animals —

osseous system — bones, 157

Attachment of voluntary and mixed muscles to bones, 158

Carlilai;i:inous condition of bones in young children and quad-
rupeds, and in certain fishes, 159

Earthy material of perfect bone, 160

Condition of bone when deprived of cartilage, 161

Condition of bone when deprived of earth 162

Reduction of bone to cellular tissue by art, 1 63

Reduction of bone to cartilage or cellular tissue by disease, 164

Ail organs reducible to cellular tissue, 165

Cellular tissue the constructor of all the organs, 166

Reunion of wounds always effected by cellular tissue, 167

The power of cellular tissue to form different organs is a mys-
tery, 168

Necessity of cartilages at the joints, 169

Articular cartilages, 170

Synovial membranes and fluid, 172

Necessity for ligaments to bind the joints, 173

Structure and functions of ligaments, 174

The envelope of bones called periosteum, 175

Extent of the periosteum — explanation of the terms perios-
teum, perichondrium and pericranium, . 176

Recapitulation of the parts and appendages of the osseous

system, 177

Necessity for tendons or parts accessory to the voluntary mus-
cles, 179

Form and arrangement of tendons, ISO

Involuntary muscles rarely have tendons — generally hollow —

muscular coat of alimentary canal, 181

CHAPTER VI.

ON THE GENERAL DIVISIONS OF THE VASCULAR SYSTEM.

Necessity for the existence of blood-vessels, 182

Of the veins, 183

Tendency of the venous blood to a common centre. — Valves

of the veins, 184

Different forms of the common centre. — The heart, 185

Conduits for the blood running from the common centre or

heart, culled arteries, 186

Communication between the arteries and the veins. — The

capillaries, 187

The circulation, 188

Gradual developement of distinct systems of organs as the

scale of animal organization rises, 189

XVI CONTENTS.

Paragraph
Partial circulation in insects, 190

Circulation, in the earth-worm, leech, marine worms, and

shell-fish, 191

Ahment in the hydra, &c. taken into the body by imbibition, . . . 192
The absorption of the nourishment from the chyme in insects,

worms, &c., is probably by a double imbibition, 193

Assimilation not complete when the nourishment or chyle is

first imbibed, hut is perfected in the blood-vessels, 194

Set of vessels, called the lactcals, for conveying the chyle to

the blood-vessels, 195

Colour and structure of chyle, 196

Origin of the lacteals. — Uncertainty of the question whether
they absorb by imbibition. — Their resemblance to roots. —

Their structure and route to the veins, 197

The agency of the lacteals in destroying the power of indepen-
dent life in the parts of the more complex animals when divided, 200
The lacteals not the only route by which substances from
without find their way to the blood. — Cutaneous, cellular,
and venous absorption by imbibition in the most perfect and

complex animals, 201

The lymphatics or absorbents. — Characters of lymph, 203

Proofs that the lymphatics convey substances to the blood, 204

Objection to the term absorbents, as applied to the lymphatics,. . 206

CHAPTER VII.

OF THE FUNCTIONS OF SECRETION, RESPIRATION, AND NUTRITION.

Recapitulation of the scale of gradual complication in the nutri-
tive organs, 207

Question why food is required to support the frame after an

animal has reached maturity', 208

Waste by perspiration in plants and animals. — Insensible per-
spiration, 209

Perspiration from the cavities. — Moisture of breath, 210

Respiration considerable in amount. — A secretion furnished

from the blood, 211

Waste of the blood by the numerous secretions. — Much food

required to compensate it, 212

Many fevers diminish the secretions and the waste of the cir-
culation— hence the impropriety of giving much food in
fevers, 213

During starvation a man lives on himself, 214

Diminution of all organs and the destruction of some less im-
portant ones, by abstinence, 215

All the particles discharged from the body are taken up by
the absorbents, carried into the circulation, and discharged
by secretion, 216

Absorption of particles carried on continually, even in health

CONTENTS. XVU

Paragraph
— reasons why the size of the organs is not diminished there-
by,— and why they grow larger during adolescence, 217

The particles of the whole body totally changed every few

years — lience the continued necessity for food, 218

The constant accumulation of worn-out particles in the blood
requires a purification of that fluid. — This office performed

by means of the secretions, 219

Numerous secretions of complex animals, 220

Folly of reasoning on the ultimate causes of vital phenomena, 221
Arrangement of the blood-vessels in secreting organs. — Mu-
cous membrane, 222

Secretory glands, 223

Arrangement of capillaries in secretory glands, 224

Structure of the ducts of the secretory glands, 225

Proofs of transpiration from the blood-vessels into the ducts of

glands 226

Economical uses made of many secretions — ^tears, saliva, and bile, 227

Of respiration, 228

Principal object of respiration,. 229

Principal ultimate elements of animal organization, 230

The surplus carbon of the blood requires to be discharged by
a special apparatus. — Partly discharged by the liver in the

secretion of bile, but not sufficiently, 231

Carbon discharged from the blood in the form of carbonic
acid, whenever the blood in living blood-vessels approaches
very near to the atmospheric air. This product always pro-
duced by respiration, 233

Animals that live in water, respire the air combined with the

water, 234

Too great a supply of air kills a fish, and exposure to pure

oxygen soon kills the more perfect animals, 235

Actual contact with air not necessary to purify the blood. —

Respiration effected by imbibition, and transpiration, 236

Cutaneous respiration of the simpler animals, 237

Cutaneous respiration in man, 238

Mode of respiration by special apparatus, 239

Resemblance of respiratory organs to secretory glands, 240

Tracheal respiration of insects, &c., 241

Aquatic respiratory apparatus, 242

Branchial respiration, , 243

Great variety of form in branchiae — all constructed on one prin-

ciple, 244

Agency of cilia in branchial respiration, 245

Pulmonary respiration, 246

Simplest forms of pulmonary organs, 247

Arrangement of the lungs in the larger animals. — Right and left

lungs, 249

Structure of the air passages in such animals, 250

Names of the principal air passage and its ramifications, 251

Resemblance of air passage to the ducts of secretory glands. —

—Their structure, 253

XVlll CONTENTS.

Paragrapli

Apparatus of inspiration 253

Air passages in the bones of birds, 254

Pulmonary and branchial respiration of reptiles,. 255

Partial respiration of inferior animals, 256

Feebleness and slowness of vital functions in animals with par-
tial respiration. — Amphibia, 257

Perfect respiration and activity of function in man, quadrupeds,

and birds, 258

Respiratory and nutritive vessels of the respiratory organs, and
the distinct routes of circulation in them. — Nutritive and re-
spiratory systems of vessels, 259

Systematic circulatory apparatus an objectionable term. — Gene-
ral or nutritive system or apparatus preferred, 260

Description of the heart, 261

Functions of the auricles and ventricles, 262

Description of the route of the circulation, 263

The heart is generally a double or quadruple organ, 266

The circulation of all animals is single and not double, 267

Interlacement of the blood-vessels. — Route of circulation when

vessels are obliterated, 268

Danger of an obstruction in a large artery. — Death of a part
inevitable when the circulation through its vessels is totally

arrested for some time, 269

Not only the life, but the activity of function in a part, depends
on the number and size of its blood-vessels and the quantity

of blood that passes through it, 270

Activity of the functions of muscles when compared with ten-
dons.— Why the rapidity of the heart's action increases by

exercise — also the rapidity of the breathing, 271

Effects of exercise in enlarging muscles, 272

Effects of rest in diminishing or destroying them, 273

Generality of the law that habitual functional activity increases
power, and habitual repose diminishes it in all the organs. —

Moral deduction, 274

Necessity for the alternation of repose and rest to promote

nutrition, 275

Of the effects of sleep at different ages, 277

Danger of over-exertion, and its effects on nutrition, 278

Effects of over-wrought labour and want of sleep 279

Agency of the organs themselves in perfecting assimilation,. . . . 280

CHAPTER VIII.

ON THE NERVOUS SYSTEM.

The variety of vital actions often performed in producing a
single effect, renders necessary a bond of communication

between the different organs, 281

First appearances of the nerves in the inferior animals, 282

Cineritious and medullary matter of the nervous system, 283

CONTENTS. XIX

Paragraph
Structure of the brain, and the terminal connections of nervous

filaments, 284

Cellular tissue of the nervous system, 285

Nervous ganglia. — Nervous filaments of the brain and ganglia.

— Functions of the ganglia, 287

Structure and function of a nerve. — The neurilema, 289

Compound nerves with compound functions. — Each nervous

fibre a distinct organ with a special function, 291

()rigin and association of the nerves of motion and of feeling.

—Effects of dividing them, 292

Formation of a nervous plexus, 293

Forming and resulting nerves of ganglia, 294

Arrangement of nervous filaments in ganglia, 295

Influence of the ganglia upon the functions of the filaments, . . . 296
Complex structure of most organs. — Extensive diffusion of
nervous filaments and nervous influence. — The functions of

<■ organs controlled by nerves, 297

Divisions of the nervous system. — Nervous systems of organic

and animal life, 299

Irregular distribution of the nerves of organic life, and irregu-
lar form of the organs controlled by them, 301

Regularity of the nerves of animal life and the organs con-
trolled by them, 303

Position and curious functions of the great sympathetic nerve

in health and disease, 304

Dependence of the nerves upon the capillary blood-vessels, 311

Mutual dependence of all parts of the frame upon each other. . . 312
Difference of plan observed between the nervous systems of
animals with an internal, and those with an external skele-
ton— Particularly in relation to the brain, 313

Still greater imperfection of the nerves in animals of yet lower

grade, 314

Consequent impossibility of comparing- the differences of in-
telligence between one great class of animals and another,
by reference to the structure of the brain or nervous system, . 316
Remarks upon the impropriety of the term — The scale or chain

of animated nature, 318

CHAPTER IX.

OF THE SURFACES OF THE BODY.

Great divisions of the human body into head, neck, trunk

and extremities, 319

Division of the head into the cranium and face, 321

Division of the trunk into chest, abdomen, and pelvis, 324

Divisions of the extremities, 328

Cellular structure of the whole body, 331

Of the integuments, 333

XX CONTENTS.

Paragrapb

Of the cuticle or epidermis, 336

Of the supposed pores of the skin, 340

Of the sebaceous folUcles, 342

Connections of the hair with the cuticle. — Growth of hair, 344

Functions of the cuticle, 348

Of the rete mucosum. — Of the colouring matter of the rete

mucosum, and the eflects of climate and seasons on the skin

and hair, 350

Of the true skin or cutis vera, 353

Of the structure and functions of cutis vera, and the papillae,. . . 355

Of the fleshy panicle or muscular layer of the skin, 358

Of the mucous follicles, 360

Connections of the skin. — Arrangement of the sub-cutaneous

cellular tissue and fat, 362

Universality of the covering of integuments, 365

Of the epithelium. — Inward reflections of the integuments. —

Modifications of the internal integuments, 366

Of the pharynx, and the muscular coat of the internal integuments, 368
Of the termination of the epithelium, and the structure of the

mucous membrane of the alimentary canal, 369

Of the villi, 371

Of mucous glands or collections of follicles, 372

Formation of the ducts of secretory glands by the integuments.

— Lining of the air passages, &c,, 374

Formation of accidental canals by the integuments, 375

Mutual convertibility of the internal and external integuments, . 376

Extent of the integuments and the surface, 379

Eflects of the absence of cuticle on the internal surface, 380

Concentration of sensibility at the origin of canals, 381

Vicarious action of the lungs and skin, 383

CPIAPTER X.

OF THE SKELETON AND ITS APPENDAGES.

Growth and general arrangement of the bones, 384

Tabular and cancellated structure of the cranium, 388

Walls, cellular structure and cavities of the long bones, 389

Cellular tissue of bone, and medullary membrane, 392

Structure of the solid portions of bone. — Use of the canals, 394

Blood-vessels of the bones, 395

Nervous sensibility of the bones, 396

A itality of bone proved by its diseases, 397

Bony structure of the head, 398

Form of tlie cavity of tlie cranium, 399

Of the frontal bone, 400

Of the frontal sinuses, 401

Of the orbitar plates, 404

Of the part of the brain covered by the frontal bone, 405

Of the parietal bones, 406

CONTENTS. XXI

Paragraph

Of the parts covered by the parietal bones, 407

Of the occipital bone, 408

Of the cuneiform process, 408

Of the great foramen, 409

Of the occipital cross, 410

Of the temporal bones, 413

Of the petrous portion of the temporal bone, 414

Of the ma«toid process of the temporal bone, 415

Of the sphenoid bone and cells, 418

Of the ethmoid bone, 419

Of the sutures, 420

Condition of the cranium during childhood, and its consequence, 421

Changes of cranium from the progress of age, 426

Good consequences of the arched form of the cranium, 427

Articulations of the cranium with the atlas vertebra, 428

Of the atlas vertebra, 429

Definition of the term condyle, 430

Articulations of the cranium and atlas with the vertebra dentata, 431

Of the limits of the motions of the head, 434

Of the bones of the face, 438

Of the upper jaw and its nerves, 439

Sympathetic connections between the teeth, the ear and eye, . . . 441

Of the teethi .' 442

Of the socket processes. — Of the enamel, 443

Of the periosteum of the teeth, 444

Of tooth-ache from inflamed periosteum, . . i 445

Of the absorption of the socket, . 446

Of the shedding of the infantile teeth, 447

Of the language of the teeth in relation to diet, 448

Of the sympathy between the stomach and the teeth, 455

Of the spine 457

Great divisions of the spine, 458

Of the bodies and processes of the vertebrae, 459

Of the articulations of the spine, and the intervertebral fibro-

cartilages, 461

Of the ligaments and spinal canal, 463

Of the mobility of the spine, 464

Of some effects of caries, rheumatism, &c. of the spine,. . . 466

Of the number and articulations of the ribs, 468

Of the cartilages of the ribs, 469

Of the sternum and its connections, 471

Of the motions of the ribs and sternum, 472

On some of the effects of mechanical restraint of those

motions, 475

Of the pelvis. — Of the sacrum, 480

Of the OS coccygis, 481

Of the ossa innominata, 482

Of the bones of the superior extremities, 483

Of the scapula and clavicle, 484

Of the shoulder-joint, 487

Of the humerus, 489

Of the elbow-joint, , 490

XXU CONTENTS.

Paragraph

Of the ulna 491

Of the radius, 492

Of the motions of the forearm, 493

Of the wrist and hand, 494

Of the bones of the inferior extremities. Of the hip joint, 500

Of the head and neck of the fenmr and its changes, 501

Of the tibia and fibula, the patella and the knee-joint, 506

Of the ankle-joint, 509

Of the tarsal bones and bones of the foot, 510

Of the ligamentous and muscular support of the skeleton, 513

Of the effects of the inelasticity of certain parts of the skeleton, 514

CHAPTER XI.

OF MUSCULAR STASIS OR EQUILIBRIUM.

Three predicates of the argument on muscular equilibrium, .... 519

On deformities produced by muscular action or debility, 522

On deformity from using the right hand, 522

On deformit}' from using the lett hand, 524

On tlie train of deformities resulting from club-foot, 525

On the train of deformities'conscquent upon sitting long erect

without support, .')29

Vices of figure from certain errors of school discipline, ... 531

Causes, effects, and cure of an habitual stoop, 535

On deformities of the eye, and vices of vision from a change

in the equilibrium of the muscles of the eye, 539

On muscular equilibrium between the muscular fibres of or-
ganic life, 546

On the reaction of the stomach and pylorus, 547

Effects of the habitual and undue distension of muscular

cavities. — Influence of this habit on digestion, 550

CHAPTER XII.

OF THE GREAT CAVITIES OF THE BODY.

Of the muscles and fleshy walls of the thorax, 554

Of the diaphragm, 560

Of the serous cavities of the thorax, 563

Of the pleuras, 565

Of the pericardium, 566

Of the position of the lungs and heart, 568

Of the structure of the larynx, 569

Of the fleshy walls of the abdomen, 577

Of the serous membrane of the abdomen, or the peritoneum, and

its arrangement, 580

Of the position of the liver, gall-bladder, and spleen, 585

Divisions of the alimentary canal in the abdomen, 590

Of the .stomach and its cardiac and pyloric extremities,. . . . 591

CONTENTS. XXIU

Paragraph

Of the duodenum, and the pancreatic and biliary ducts,. . . . 593

Of the small intestines, 594

Of the ccEcal valve, 596

Of the coecum and colon, 597

Of the vena porlce and portal vessels, 599

Functions of the portal vessels, GOO

Effects of compression on the circulation in the portal system, , 601

CHAPTER XIII.

OF THE MECHANISM OF BREATHING.

Action of the muscles of the chest in inhalation, 605

Action of the diaphragm and abdominal muscles in inhalation.

— Movements of the abdominal viscera and heart, 609

Forces producing- exhalation, 610

Effects of muscular debility on breathing, 611

Action of the abdominal and cervical muscles in difficult breathing, 612

Effects of mechanical restraint on breathing, 613

CHAPTER XIV.

REMARKS ON DIGESTION AND THE CIRCULATION.

On the importance of mastication, 619

Effects of loss of tone on digestion, 622

Phenomena attendant on stomachic digestion. — The siesta, 624

Water probably absorbed from the stomach by the veins, 625

Duodenic digestion.^ — The peristaltic motion, 626

Effects of poisons and emetics. — Erroneous notions about bilious-
ness, 627

Structure of the blood-vessels, 630

Essential or serous coat of blood-vessels, 630

Thick fibro-cellular coat of blood-vessels, 631

Middle or fibrous coat of the arteries. — Its functions, 632

Effects of active exercise on the circulation, 634

Effects of passive exercise on the circulation, 639

CHAPTER XV.

ON THE FUNCTIONS OF THE NERVES AND BRAIN.

Proof that the function of a nervous fibre resides in all parts of

the fibre, 640

Proof that consciousness and will do not reside in the nerves of

the senses, , 645

General description of the brain and its membranes, 648

Argument to show that consciousness and will are not functions

of the organization, Q59

XXIV CONTENTS.

Paragraph
Proof thai the display of the mental functions does depend on the

organization of the brain, 668

Question of a common centre of the nervous system or a senso-

rium conmiune, 669

Ganghonic character of the brain, 670

Gradual developement of the brain in ascending the scale of

organization in tlie vertebrate animals, 672

Gradual progress of the developement of the brain from infancy

to age, 675

Fundamental principles of phrenology. — Their occult character, 680

Of the spinal marrow — its position and extent, 681

Internal arrangement of medullary and cineritious matter, . 682

Distribution of the fibres of the spinal marrow to the brain, 686
Proof of the existence of divergent nervous fibres entirely confined

to the brain, 690

Membranous arrangement of the convolutions of the brain, .... 691
Proper mode of investigating what are the functions of the nerves

of the brain. — Errors of tlie phrenologists, 692

Phrenology not dependent on eranioscopy. — Origin of cranioscopy, 703

Sources of error in cranioscopy, 707

CHAPTER XVI.

OF TEMPERAMENTS AND IDIOSYNCRASY.

Nature of temperaments, 710

Of the sanguine temperament, 717

Of the bilious teniperament, 722

Of the lymphatic or phlegmatic temperament, 724

Of the nervous temperament, 725

Of a peculiarity of temperament in women and children, 727

Changeability of temperament, 728

Of peculiar temperaments of particular organs, and their con-
nexion with idiosyncrasy, 730

Questions for pupils, 305

Glossary, 334

PHYSIOLOGY FOR SCHOOLS.

CHAPTER I.

ON THE MOTION AND GROWTH OF ANIMATE AND INANIMATE
• BODIES.

1. When we examine the great mass oi things which
nature continually presents to our observation, w^e soon
learn to classify them into things which have life, and
things which have not life. Now what constitutes the
difference between these two great classes of things ?

2. The first living things which strike the attention of
an infant, are observed to move from place to place with
perfect freedom, and thus his earliest notion of life is
connected with motion. His mother's lap-dog or his
favourite kitten goes to sleep upon the hearth-rug, and
the child is alarmed lest it be dead. His father holds a
watch to his ear ; he sees the second-hand jerking and
turning round, he hears the click corresponding with
every jerk, and very naturally inquires, "Is it alive?"
He soon learns, however, that to seem to he still is not to
be dead, and that to 7nove is not always to he alive.

3. Still, he finds it difficult to separate entirely the
ideas of motion and life in many cases. He knows that
the trees are living, even when not a leaf trembles in
the quiet air of a summer noon. " The wind does not
blow, and why should they move?' Yet I have knowr*
many intelligent youths who, though they would blush
to be called uneducated, were extremely puzzled with a
very simple experiment. When an eye-stone, as it is
called, is olaced on a smooth plate, with a little weak

(25)

26 MOTIONS OF THINGS.

vinegar, it is soon surrounded by small bubbles of air,
which escape from beneath it, and it gradually moves
from place to place, seeming to crawl round the plate.
I have often known these bubbles to be mistaken for
legs, and the eye-stone for an animal. It is, in truth,
nothing but a plug or door, constructed by a peculiar
kind of marine shell-fish, to shut out unwelcome visiters
when the animal wishes repose. It scarcely differs in
nature from Hmestone or marble, and either of these
substances, if cut into the same form, and polished, will
behave in the same manner : any chemist will tell you
why.

4. Perhaps next to motion, the phenomena of growth,
as witnessed in hving things, arrests most forcibly the
attention of the child. He sees that he is small, and
that his parents are much larger : they inform him that
they were once as small as he. His own growth, from
day to day, becomes a matter of pride with him, and he
sighs for the time when he shall be as large and strong
as his father, that he may be able to protect his mother,
his sisters, and himself The shrub in the garden, the
grass in the field, and the leaves and branches on the
trees, all put forth in his presence, and gradually assume
their proper form and size. He is told that these thingr.
are alive, and naturally concludes that whatever grows
has life.

5. But here, again, his ideas are soon confused by
newly acquired facts. On the one hand, he observes
that plants and animals, or, in other words, all things
which have life, continue to live even after they have
ceased to increase in size ; and, on the other, he per-
ceives that many things which, as he is told, are not
alive, are seen to grow ; so that he is not always able,
if not instructed, to perceive the diflference between the
growth of a living thing, and that of a thing which is not
alive.

6. When very young, he may observe the icicles,
pendent from the eaves of houses, gradually increasing
in length by a process which he does not understand.
Sometimes even this simple phenomenon has been mis-

GROWTH OF THINGS. 27

taken for the result of life ; but the error is confined to
that early period of infancy when the fall of snow is
attributed to " the Welshman picking his geese."

7. At an age a little more advanced, the child ob-
serves, perhaps, that the flowers in the vase on the
mantel-piece continually drink up the water in which
they are placed ; and, as they drink, their young leaves
grow longer, and their buds expand. He places his
dry sponge in a basin, and he observes that it slowly
draws in the water which surrounds it, and, as it does
so, swells out until its bulk is prodigiously increased, and
its form entirely altered. Now there is sufficient resem-
blance in these two occurrences to lead the very young
inquirer to ask wherein consists the difference. I have
heard the question not unfrequently, and always from
the most intelligent children.

8. But, my young readers may remark, we are no
longer such children, that we need be cautioned against
these mistakes. Perhaps not. Yet there are others of
a similar nature w^hich occasionally confuse heads much
older than yours. You have read of the beautiful in-
crustations of brilliant spars which hang from the roofs
of caves in many parts of the world. The island of
Antiparos, for instance, the Peak of Derbyshire, or the
mountains of Virginia. You know that these spars are
continually growing, and that they not unfrequently
assume a rude resemblance to animals and plants.
Again; if you have ever been in an old and damp
house, you may have seen the plastered walls covered
with patches of saltpetre. This mineral substance
shoots out into a delicate efflorescence so nearly resem-
bling moss and mould, that you must examine closely
before you can distinguish it from them. Moss and
mould are true plants, which may be sometimes seen
growing on the woodwork of the same apartment. Jf
you brush away both the mould and the saltpetre, they
will soon grow again, side by side, so that you can
scarcely be blamed for mistaking the one for the other.
In the neighbourhood of certain iron-works, where the
ore is of a pecuhar quality, lying in low and damp

28 GROWTH OP THINGS.

ground, it is sometimes entirely exhausted by the
demands of the furnace; yet, after the place has been
deserted for a few years, in consequence of the failure
of the supply, the proprietor is surprised to find a new
bed of ore in the old place; and the operation of the
works is then profitably renewed.

9. Now the facts just mentioned, and others which
resemble them, produce a vague impression that rocks
and stones possess a kind of inherent power of increasing
their own dimensions; a power which, from our last
deduction (4), seems to belong exclusively to living
things. You may be already too well informed to
entertain such a strange opinion, but you must now be
prepared to grant that not all that groivs has life.

10. Motion and growth are the only phenomena
which strike the eye of the youthful observer, as ex-
hibited by all living things without exception ; and these,
as we have seen, are insufficient in themselves to furnish
a distinction between such things and those which have
not life.

11. Birth and death are often mentioned as pecuhari-
ties of living things ; but birth is but the beginning of
independent life, and death is but the end of hfe. Neither
of these are properties of living things; for birth has
passed away the moment any thing begins to live inde-
pendently, and the thing must cease to live the moment
that death occurs. I wish to confine your attention in
this chapter, to things as they are — not as they have
been, or will be hereafter. Although neither motion nor
growth, which is but the result of a very slow motion,
are confined to living things, we must endeavour to find
such peculiarities in the motion and growth of these
things as will enable us to distinguish them from those
which have not life. By so doing, we shall take our
first step in the study of physiology, which is the name
given to the science that treats of the actions of living
things and the parts of ivhich they are composed.

12. I must take it for granted that you have already
acquired a knowledge of the laws of attraction ; that
you are aware of all we know of the reason why a

PECULIAR MOTIONS OF LIVING THINGS. 29

stone falls to the ground, and why a spring, when bent,
flies back, and continues vibrating for some time. If
you are ignorant of these things, inquire of your teacher
or your parents ; for an acquaintance with the laws of
attraction, as displayed by inanimate matter, is a neces-
sary prerequisite to the comprehension of the simplest
physiological facts and doctrines.

13. Then, let us examine wherein the motions ob-
served in living things differ from such as characterize
those things which have not life. The latter have no
power of moving by their own energy or will. Their
changes of form and position are all the result of forces
which act upon them from without. They must be
placed under the influence of other things before they
can alter their condition in the slightest degree. Let us
give some examples. A stone would not fall to the
ground, were it not that it is attracted towards the
earth, and the earth towards it. The spring could
never vibrate in consequence of the attraction of its
particles for each other, were it not that the hand, or
some other external agent, has previously bent it from
its natural position. It cannot vibrate of itself. The
force with which it recoils is never greater than that
which is applied to bend it ; and when this is expended
it ceases to move. The watch (2) no longer clicks, and
its hands are at rest, the moment that the spring has
lost the curve communicated to it by the key. The
eye-stone (3) cannot crawl around the plate without the
presence of the acid, which, as your preceptor will tell
you, if you have not studied chemistry, combines with a
part of its substance, disengaging from it a kind of air
or gas. This gas, by escaping in bubbles from beneath
the stone, pushes it along. When all the acid of the
vinegar has combined with the eye-stone, leaving no-
thing but the water and the dissolved portion of the
stone around it, its motion ceases, because no more gas
escapes.

14. Now living things are moved in the same manner
by external causes ; for, if a man be hanged and the
rope break, he will fall to the ground like a stone : if

80 PECULIAR MOTIONS OF LIVING THINGS.

the limb of a tree be bent by the wind, it will fly back
and vibrate like a spring. But there are other kinds of
motion observed in living things, that are never seen
performed by things which have not life.

15. Most of you may have seen potatoes sprouting in
a dark cellar. If so, you may have noticed how^ all the
young roots take their course towards the neatest moist
earth, and how regularly and rapidly the tender vines
crawl toward the crevice in the wall which admits the
strongest light. There "are persons who will tell you
that the roots are attracted by the w^ater, and the stems
by the light ; but such persons have a very vague idea
of the meaning of the word attraction, as employed by
philosophers. Your preceptor can inform you, or, when
you become acquainted with the elements of mathe-
matics and natural philosophy, you can inform your-
selves, that light, which is an imponderable substance,
cannot exercise an appreciable attractive power upon
even the most minute particle of matter that is capable
of being weighed by human hands. There must there-
fore exist in the living vine and roots some internal and
inherent powder by which they move in certain direc-
tions in preference to others, as if by vohtion — a power
that is not the result of actual forces from without, such
as produce the motions of inanimate tnatter.

16. All living nature teems with evidences of motion
originating from internal power of this kind, by means
of which every thing that has life undergoes changes
which can never be imitated by inanimate matter. I will
mention a few striking examples. The leaves of almost
all plants turn their upper or deep green surfaces to the
light, and follow, with more or less regularity, the appa-
rent motion of the sun in his daily route.

"The sunflower turns on his god when he sets
The same look that he turned when he rose."*

Most flowers open their petals in the morning, and shut

* Although the propensity of the sunflower to follow the course of the
sun is only remarkable when the plant is in vigorous health, and is even
then imperfectly displayed in many cases, any one who will compare the
direction of the same flower at ten in the morning and five in the after,
noon, will be convinced that this propensity is no poetical fiction.

PECULIAR MOTIONS OF LIVING THINGS.

them in the evening, to protect the more tender parts
from the night dews and the cold ; the primrose prefers
unclosing in the twilight, and folds its delicate veil in
the morning to exclude the heat ; while the night-bloom-
ing cereus displays its glories only to the moon and stars,
expanding at the " noon of night," and fading before it
sees the day. Most of you may have seen the sensitive
plant, of which not only the leaves, but even the branches
recoil the moment we touch them. The plant called
Venus's fly-trap, (Diongea Muscipula,) has a part of the
extremity of its leaves constructed somewhat like a
steel-trap, which closes instantly and crushes or im-
prisons any small insect which has the rashness to alight
upon it In fig. 1, you are presented with a sketch of
this curious plant. At a, you see a leaf expanded, and
the darker part, situated in the centre, cannot be touched
in the gentlest manner, w^hile the plant is vigorous, with-
out causing the leaf to close. At h, you see a leaf that
has entrapped a fly.

Venus's Fly-Trap,

32 APPARATUS ORGAN.

17. In animals, we observe still stronger evidences of
motions originating from internal causes ; for every
known animal enjoys the faculty of will, and changes
its form or its attitude to suit its own convenience. Till
within a few years, some learned naturalists believed
that many of the simpler animals were deprived of will
and feeling, but more recent discoveries have proved
the error of this opinion.

18. I think you will now be prepared to grant that
living things possess a power of regulating their own
motions to a certain extent : that they seek what they
require, whether it be light, heat, water, or comfort, by
powers peculiarly their own. But if you be still in-
clined to doubt this proposition, — and it would not be
unnatural for you to do so in the case of plants, which
are deprived of will and feeling, — you will soon be con-
vinced in the sequel. Now, no such power is possessed
by any thing that has not life : and here you see a broad
and clear distinction between the two great classes of
things mentioned in the beginning of our argument.

19. The power of which we are speaking evidently
resides within the living thing which is endowed with it ;
and, as it produces mechanical motions, there must be
within every thing which has hfe an apparatus — a ma-
chine to produce these motions ; — for no mechanical
effect can be produced without a machine. But almost
every living thing performs various different acts ; and a
machine which is intended to perform various acts, is
usually composed of many different parts. -Let us take
a rose-bush for an example. It has a root to supply it with
nourishment, a stem and branches to support the leaves
and flowers, seeds to produce other rose-bushes in suc-
cession, &c. Again, from among animals let us take a
cricket. It has wings to fly and sing with, legs to leap
with, jaws to eat, and a stomach to digest its food with,
eyes to see with, antennae, or feelers, in which reside
the sense of touch, and, perha/ps, the poicer of conveying
its ideas, &c. Now each of these parts of the ma-
chine, which performs some distinct act or purpose, is
called an of^an.

ORGANIZED BEINGS ORGANIZATION. *>3

20. But things which have not Hfe perform no such
independent naotions or acts ; they therefore have no
organs. For this reason it has beconae customary to
distinguish things which have hfe by the title of organ-
ized beings.

21. You may naturally suppose, since organized
beings are endowed with powers superior to those which
have not life, that the former class of things must be
formed of a different kind of matter from that of which
the latter are constructed ; but this is not the case. All
the parts of a living or organized being, and all the
materials for its growth and support, are derived from
the general mass of things which have not Hfe. Yet
this matter must be arranged in a totally different
manner from that in which it is found before it becomes
possessed of life ; for otherwise it could not be fitted to
perform such different offices : and here I must give you
another definition. The peculiar arrangement of the mat-
ter which forms a Hving thing, is called its organization.

22. You know that when an organized being dies, it
soon begins to decay ; but one part decays much faster
than another. The wood of a dead tree long outlasts
the bark and the leaves, and the bone of an animal
remains when the flesh and skin have disappeared.
Sometimes we can see the disorder in the organs which
produces death, but on other occasions it cannot be dis-
covered, and in such cases no perceptible change takes
place in the organization of the dead tree or animal for
a considerable time. Yet the mysterious principle of
life, — the power which kept the machine in motion, — has
departed, we know not why. We can no longer call
the body, or the part of it which has not yet decayed,
an organized or living being, for its life or being has
escaped from it. But its organization still remains,
wholly or in part. Its arrangement is such as life alone
could effect, and death itself cannot instantly destroy.
These remnants of things which have had life are still
organized, though dead, and are very different from
things which never had life : they cannot return to the
condition of these latter things until they have becoms

3 ^

34 ORGANIC AND INORGANIC MATTER.

entirely decayed. You will now understand why we
divide all matter, whether dead or living, into two great
classes ; organic matter ; which has life, or has had it so
recently as not entirely to have lost its character; and
inorganic matter; which never had life, or which has
been so long dead as to have lost all traces of its fornner
organization.

23. Sometimes the whole or a portion of an organ-
ized being becomes buried in the earth or inclosed in
rocks, during great convulsions of nature, or during the
slow deposition of the stony matter which is often dis-
solved by the waters of springs, streams, or floods ; and
the forms of such beings are continually found in the
bottoms of old caves, in solid rocks, and other similar
situations. These remnants often preserve a part of the
organic matter of which they were formed when alive.
Thus, the bones of the mammoth of America, so con-
stantly discovered about the salt-licks of the western
country, and sometimes even in the sands of New Jersey,
are always found to contain a considerable portion of
animal matter, though ages have passed since their
death. The same remark is true with regard to the
bones of the rhinoceros, the tiger, the hyena, &c. so
often found in countless numbers in the bottoms of caves
in Europe. But most of the shells which form a large
portion of certain limestone and other rocks, and which
we commonly call petrifactions, have lost entirely the
matter of which they were once composed. This has
been washed away, and another substance deposited in
the cavity thus made in the rock ; so that the form alone
i/ preserved, and the petrifaction is composed entirely
of inorganic matter. On the coast of Florida there are
found whole reefs of coral that were once constructed by
myriads of minute animals living in the sea, and v^'cre
then composed principally of lime. These reefs have
been lifted up from the water by some earthquake, or
other great convulsion of nature, occurring many hun-
dreds, perhaps thousands of 3^ears ago. They still re-
tain all the delicate forms of coral, though apparently
converted into beautiful calcedony or cornelian, which

ORGANIC REMAINS SYSTEM. 35

is a kipd of precious stone composed chiefly of silex or
sand. Even the softer parts of animals and plants are
often thus completely petrified ; but though all their
organic matter has decayed and past away, these casts
of things which once had life are still known to writers
on natural history by the title oi organic remains;^ term
more properly applied to those relics in which some part
of the organic matter is still traceable.

24. Those organized beings which are somewhat
complex in their structure, have occasion to perform
many acts which are also complex, and require the
assistance of many organs acting in concert. Thus,
man, in moving from place to place and performing
mechanical operations, requires the use of most of his
muscles. In examining the properties of any thing which
interests him, he often has occasion to see it, feel it, taste
it, &c. Now you have doubtless learned already that
the senses by which we perceive the properties of things
are all dependent on a class of organs called the nerves,
I do not suppose that you have yet a clear idea of what
is meant by a muscle or a nerve : these things I shall
describe hereafter: but I allude to them here only to
explain the meaning of another term which presently I
shall have occasion to use. Any set of organs which
are employed in accomphshing one common purpose is
called a system. Thus we have the muscular system
for motion, the nervous system for perception, and many
others.

25. The word system is commonly employed in con-
versation to signify the whole frame or body of an
organized being ; and you have no doubt heard very
sensible people say, when the doctor and they disagree
as to what is proper for their health, " I know my own
system. Every man best understands his own system."
Now this is a very vague use of the term. It confuses
the mind, and it is better to avoid it while engaged in
studying this little volume.

26. Having now explained wherein the peculiar mo-
tions of living things, or organized beings, differ from
those which are common to them and to inanimate

36 MODE OF GROWTH IN LIVING THINGS.

matter also, and having given you a few ne(^essary
definitions of terms, let us proceed to examine, in the
same general and introductory manner, the differences
in the mode of growth between organic and inorganic
bodies.

27. To obtain a clear idea of the mode in which
inorganic bodies grow, I will tell you of a pretty little
experiment which you may try for yourself on a suit-
able occasion. Get a good large lump of alum ; put it
in a suitable vessel, and pour upon it some boiling
water, but not enough to dissolve it all. Let it simmer
before the fire for a quarter of an hour. Then pour the
boiling water off into a clean oil-flask. Keep the fluid
hot by placing the flask on the ashes, or over a lamp,
till you have time to tie a string round a small piece of
solid alum, and suspend this in the flask, near the bot-
tom. Then set the flask in a cool place, and you will
see the small piece of alum growing with rapidity as
the fluid cools. And if you are careful not to let it cool
too fast, you will see that the alum grows by covering
itself all over with beautiful little crystals which are
continually increasing in size. Even upon the string,
you will often perceive other crystals which seem
to grow there spontaneously. Your preceptor has no
doubt explained to you, ere this,, the nature of crys-
tallization, but I wish to call your attention to the fact
that all the growth of the piece of alum is produced by
the deposition of more alum upon the outside of it. Not
a particle has passed into the interior of the lump. Nor
has there been any change produced in the nature of
the lump, or the matter added to it. The lump is still
alum, and all that has been added to it is no more than
so much alum, which has been taken from another
piece of the same substance and conveyed to this by
the w^ater. Such is the nature of growth when it takes
place in any inorganic body whatever. It is true that
all such bodies do not crystallize, but their growth is
always the consequence of the addition of particles
upon their external surface, and whatever they gain must
be lost by some other portion of the same kind of mat-

MODE OF GROWTH IN LIVING THINGS. 37

ter. They never have the power of selecting different
materials and converting them into particles of their
own nature, so as to appropriate them to their own use.

28. Now the history of the growth of organized
beings is the reverse of all this. Neither a plant nor
an animal ever grows by the addition of particles
applied from without upon its surface. The bark of the
tree increases in thickness as the tree grows older,
because every year a new layer is formed on its inner
side. The external false skin or cuticle of an animal is
continually wearing off; as in man ; or it is regularly
burst and pushed off bodily at stated intervals ; as in
snakes, crabs, and the silkv/orm, which shed their
coats; yet as frequently is a new skin produced be-
neath that which is loosened or torn off, and this is
formed of matter from the interior of the animal.

29. You see, then, that as the growth of all living
things takes place within their substance, it is necessary
that the materials for their growth, which are only to
be found without, should enter into the interior and
penetrate their substance in all directions to reach the
various parts which are continually growing.

30. A tXQQ absorbs its food from the soil. This food
consists of water, in which is dissolved a variety of
salts. It also absorbs certain kinds of air by its leaves,
and these substances combine with each other in such a
manner as to form the sap, which nourishes the tree.
Man lives upon the bodies of other animals and plants,
which he takes into his stomach. The sides of a canal
connected with the stomach absorb such parts of this
food as are fitted to support the frame. Man also
absorbs certain kinds of air by means of his lungs in
breathing, and these substances combine with each
other in such a manner as to form the blood, which
nourishes him.

31. Now, out of the same sap, the tree must form bark
in one place, wood in another, its fruit in a third, &c. ;
and out of the same blood, the man must make skin in
one place, a muscle in another, a nerve in a third, &c.
Hence you perceive that organized beings possess the

38 MODE OF GROWTH IN LIVING THINGS.

power of changing other things into their own nature,
and are able to construct for themselves the particles
necessary for their growth.

32. In order to make so many different parts out of
the same sap or the same blood, the plant or animal
must possess the power of moving the nourishing fluid
from place to place, wherever it may be needed ; and this
fact must remove all doubts that you may have enter-
tained as to the existence of an independent power of
motion peculiar to organized beings (18); so that you
can now comprehend with clearness the broad differ-
ences existing between things which have life and things
ivhich have not life.

33. Before we quit this subject entirely, however, I
must explain a few apparent exceptions to the rule laid
down in paragraph 27. You remember our little com-
parison between the sponge in a basin and the flowers
in a vase (7). Both seem to grow by the same pro-
cess. Now the sponge was once part of an organized
being : it still contains a good deal of organic matter ;
but it has been long dead, and possesses no powers but
such as properly belong to inorganic matter. Yet it
seems to grow by drinking up water, or, in other words,
by receiving food into its interior, just like the flowers.
I can show you, however, that it does not grow, and
that the flowers do. Take your scales, and weigh first
the dry sponge. Instead of the open basin used in our
first experiment, take a ground stopper glass jar nearly
full of water. Weigh it, and mark the height of the
water in the jar very exactly, with a piece of greased
charcoal. Now put in the dry sponge, and let it seem
to grow. Next day you will find the sponge fully ex-
panded and very large. Yet the water stands at exactly
the same height that it did before, and the whole appa-
ratus weighs just as much as the bottle, the water, and
the dry sponge taken together did weigh before the
experiment. You may change the water, filling the jar
to the same mark every day, as long as you please, yet
the weight of the whole will remain the same. Now
take the sponge out of the water and dry it. You will

MODE OF GROWTH IN LIVING THINGS. 39

then find that it weighs exactly as much as it did at
first. It has not grown a particle by admitting other
matter into its interior.

34. To compare the effects of water on a sponge
with those which it produces on a plant or flower — take
a narrow-necked flower- vase, and fill it completely with
water in the spring of the year, or in a warm room in
winter; weigh it when thus full, and note the weight.
Then choose the bulb of a hyacinth, of such size that it
will just cover the top of the vase without falling into it,
but so rounded that the bottom of the bulb will sink half
an inch or more into the water. Weigh this bulb also,
and note the weight. Then add the two sums together,
and preserve the remembrance of the amount. Now
set your bulb on the vase, with its large end in the
water, and supply it daily with fresh water. You will
soon see the roots growing rapidly downwards until
they seem almost to fill the vase, while, in a few days,
the leaves will shoot and expand from the smaller end,
and at last the flower-stem with its buds will spring up,
and the flowers will bloom. If you weigh the vase,
together with the plant, from time to time, you will find
it continually growing heavier and heavier; thus show-
ing most plainly that the plant has converted a portion
of the water (perhaps with certain salts, or other im-
purities, which are always found in water that has not
been distilled,) into matter fitted to form part of itself,
and has appropriated this matter to its own use.

35. All the cases of seeming growth by absorption
which we witness in inanimate matter, resemble the
case of the sponge in the foregoing experiment. Let
us take the case of an iron bar, heated in a forge at the
blacksmith's. You see that the hotter it becomes, the
larger it grows. But this is entirely owing to the ab-
sorption of heat by the iron, as water is absorbed by the
sponge. When the iron is taken out of the furnace, the
heat leaks away or flies off, till it is as cool as the air
around it; just as the water flows out, or evaporates,
when you hang the wet sponge in a dry place.

36. You see, then, that unlike things which have not

40 NATURE OF LIFE.

life, all organized beings possess a power of moving
to seek what they want, moving their nourishment from
place to place within them to supply the growth of their
different parts, and moving even their solid particles in
such a manner as to make room for the other particles
by which their size is gradually increased. This power
resides within themselves. This power is life.

37. Of the nature of life we know nothing. An ani-
mal dies : its body is still composed of organic matter.
At the moment of death it does not undergo any change
that we can discover. It only ceases to move. Yet the
power residing within it has departed ! Then what is
this power 1 Every child has asked himself the ques-
tion, but it has never been answered. We know it only
by its effects. When an animal or plant is labouring
under its last illness, (for plants can be sick as well as
animals,) the effects of life grow weaker and weaker.
But what becomes of life itself? Does it cease to exist
when it ceases to move the body ? The Scriptures tell
us that the Creator, after he had completely formed
man, breathed into his nostrils the breath of life. That
is, he put in motion the body he had formed. Whether
he still maintains that motion by his own direct influence,
or whether he acts through one or many agents in pro-
ducing such eflects, we know not, for he has not shown
us. I must beg of you to remember this through life.
We never can know any thing of the first link in a
chain of causes and efiects, unless instructed directly by
the Great First Cause of all things. By remembering
this, you will escape the danger of being led astray by
the thousand follies of the wise, when they attempt to
lead us beyond the boundaries of human- learning —
follies which I most fervently desire to escape in writing
this little book for vour instruction.

CHAPTER II.

ox THE INDIVIDUALITY OF ORGANIZED BEINGS, AND THE
DIFFUSION OF LIFE IN LIVING BODIES.

38. Every part of an organized being enjoys the
privilege of life, for every part possesses the power of
regulatinor its own motions in such a manner as to
choose the particles which are required for supplying its
own grow^th, and to place them in their proper positions.
Now, all such beings as are a little complex in their
structure, are composed of many organs, each of which
performs a distinct office. Thus ; the eye of a man is
made for seeing, and the flower of a tree is designed to
produce the fruit. In the ordinary course of events, the
finger does not see, neither does the leaf bear fruit.
These organs, therefore, require peculiar powers of life,
or, as we term them, peculiar vital powers.

39. The appropriate acts of the several organs are
called X\\e\r functions ; and when we speak of all the acts
of all the organs of an animal or plant, we term them
the vital functions. Thus it is the function of the eye to
see, that of the ear to hear, that of the mouth to speak,
and that of the flower to protect and foster the young
fruit.*

40. Though every organ in a complex living body

* (To teachers.) — The term vital function is used by some eminent
writers in a more restricted sense, to signify those functions only that
are common to all living things, as distinguished from those deemed
peculiar to animals, such as sensation and voJuntary motion. So far as
these latter functions are dependent on the organization, they are as
purely vital as any others observed in living bodies ; and as the restric-
tion of the wider meaning of the term is calculated to lead to false im-
pressions as to the real importance of certain parts of the animal frame,
I have declined attempting it.

42 MUTUAL DEPENDENCE OF PARTS

enjoys, as you perceive, its own peculiar mode of life,
(38,) yet it does not follow that, if separated from the
body, it could continue to live when thus deprived of
the assistance of other organs. The stem of a tree
does not flourish when deprived of its roots and left in
a situation where it cannot form new ones ; for, although
it possesses the power of propelling the sap that causes
it to grow^ and enables it to shoot out branches, leaves,
and flowers, yet it is unable, in most cases, to keep up
the supply of sap. The stem does not perform the
functions of the roots. Hence you understand that, in
complex plants and animals, if any important part be
"wanting or out of order, the whole organization suffers;
or, in other words, the health of every part is necessary
to the health of the whole, and no one function can be
impaired without embarrassing all the functions.

41. But you are aware that all parts of a plant or
animal are not equally important. For a man can very
well spare an arm or a leg, and his health may not ap-
pear to be injured by the loss. It would even seem that
by lopping olf part of a plant we improved its vigour ;
for we trim our vines in the spring of the year to make
them bear more grapes. When, however, you remove
or divide any very important organ, the being generally
dies. If you cut off a man's head or open his heart,
he sinks immediately ; and if you pass your knife or
your axe all around the trunk of a tree, so as to divide
the inner bark quite through to the wood, the tree soon
withers. This is the way in which the w^estern farmer
begins to clear his land of the forest.

42. Even a small wound, or the removal of an unim-
portant part, would almost always kill the plant or
animal, sooner or later, were it not that the vital func-
tions of every living thing enable it to heal such injuries.
For, as all that lives requires food to supply its growth
and support its frame, and as this food is always con-
verted into sap or blood, which are fluids and run out
when the body is wounded, a very small cut, if allowed
to remain permanently unclosed, would be sufficient to
exhaust the supplies on which the continuance of life

LESS MARKED IN SIMPLER ANIMALS. 43

depends. We often see this proved when the peculiar
health or condition of the plant or animal prevents a
wound from healing. A small cut in the bark of a
grape-vine when the sap is running, in the spring of the
year, will sometimes cause it to bleed to death; and
there are many cases recorded by surgeons, in which
man has suffered in the same way from the scratch of
a pin, or the extraction of a tooth.

43. Now the power possessed by different organized
beings to heal the injuries which they receive by acci-
dent, appears to be greater exactly in proportion to the
simplicity of the structure of the injured being. Man is
the most complex of all animals, and if you cut him in
half, both pieces will die, but if you serve a common
earth-worm in the same manner, it is said that the
pieces both heal at the wound, and each piece may
continue to live as a separate worm.

44. There are animals, much simpler in structure than
man, that will die after their heads are cut off, but many
of them, though they cannot live long enough to make
themselves new heads or new tails like the earth-worm,
are yet capable of moving, and performing many vital
operations. You all know how long the tail of a snake
will curl after it is cut from the body ; but I have some
still stranger stories to tell you. When the hind legs
of bull-frogs have been cut off, skinned, and placed over
the fire to be cooked, they not unfrequently ^^hop out of the
frying-pan into the fire. " I was once dining very com-
fortably on some soup made from a large snapping-turtle
that had been beheaded on the preceding day, but being
extremely startled by the loud howling of a favourite
dog in the yard, I ran out to see what was the matter.
Poor Caesar was whining piteously, and stood looking
intently at one spot on the ground, with an air of
extreme bewilderment. I went to examine what had
^^ puzzling set his puppy brains," when, behold ! there lay
the head of my snapper, with the end of the dog's nose
fairly bitten off by its jaws while the poor animal had
been innocently smelling after his share of the dinner.

45. A tortoise will live for a long time when deprived

44 ORGANIZATlOrf OF THE FLUIDS.

of both its brain and its heart. When an unfortunate
shark has fallen into the hands of its cruel enemies, the
sailors, it is frequentl}^ opened and cleaned while still
alive; but, although taken from its natural element and
treated in this manner, it will still make formidable battle
with its jaws and tail, sometimes for hours afterwards.

46. Thus, you perceive that in proportion to the sim-
plicity of the structure of an animal, the powers of life
seem to be more equally diffused through every part,
and the health of the whole becomes less decidedly
dependent on the health of each of the parts. Having
arrived at this conclusion, you will be less astonished at
what will be stated hereafter.

47. Even the fluid parts of animals and plants are
said to be organized ; and, from the moment at which
food is taken in by the roots or the stomach, it under-
goes continual changes, until the part that is fitted to
nourish the body is converted into perfect sap or blood,
and carried to the difierent organs for their sustenance.
These changes bring about a continually increasing
resemblance between the part of the food which is thus
appropriated, and the substances of which the body and
its various organs are composed ; and the process by
which they are accomplished has been termed assimi-
lation,

48. When the assimilation of the food is completed,
as far as possible by the roots, or the stomach and bow-
els, the fluid formed by it no longer resembles in its
nature any thing that is found in the inanimate world.
It constitutes a part of the living being from the mo-
ment when it is received within the body, and the
actions of life cannot be maintained without its pre-
sence. There is strong reason to believe that this fluid,
like all other parts of a living body, partakes of the
powers of life ; or, in other words, fulfils its own vital
functions.

49. I shall not attempt to enlarge upon this subject in
addressing young beginners in physiology ; but it is ne-
cessary to mention a few facts, to show that the fluids
are extremely simple in structure in the simpler animals
and plants, but become much more complex in those

ORGANIZATION OF THE FLUIDS. 45

which are composed of many organs, and are destined
to fulfil a large circle of usefulness. The sap of most
plants is composed chiefly of water, and the proportion
of other matter contained in the fluids of those which
rank lowest in the scale of nature is very small ; but it
is much larger in many of the trees and other vegeta'
bles that produce large quantities of gum, resin, sugar,
meal, and other materials useful to man. Plants, it is
true, never reach that high degree of complexity in their
organization, which we see in the most important ani-
mals ; and, therefore, you will not be surprised to learn
that the sap contains very little matter that seems to be
distinctly organized, even when examined under the
microscope. But in the sap of the somewhat extensive
group of vegetables that pour out a milky juice when
wounded, we may detect, by the aid of strong lenses, a
number of distinct solid globules ; and these globules,
being a product of life unlike any thing existing in inani-
mate nature, cannot be regarded as other than organized
bodies.

50. The substances which form many of the plants that
have just been mentioned, bear a stronger resemblance
to animal matter than those which are found in most
vegetables ; for they contain a peculiar kind of gas
{nitrogen) which was formerly supposed to be confined,
among living things, to animals alone. But it is not our
intention to enter farther than is absolutely necessary
into the consideration of the chemical structure of living
things, or into the subject of vegetable physiology.

51. Now the simpler races of animals, like most
vegetables, are nourished by juices composed chiefly
of water, combined with a very small portion of salts
and earthy matter, and although we call these juices by
the general term of blood, yet they present a very dif-
ferent appearance from blood as it is found in the more
complex animals, nor has any thing resembling the solid
globules been certainly detected in all of them.

4 *

ORGANIZATION OF THE MEDUSA.

52. At fig. 2, you see Fig. 2.
the representation of a cu-
rious and very beautiful
animal, of a tribe which
naturalists have generally
termed a Medusa, because
most of the animals of this
tribe are furnished with
long snake-like tendrils,
which will sting severely
when they are touched.
You have heard of the
'phosphorescence of the sea,
— the light that is emitted
by the waves of the ocean
when agitated — which is
often very brilliant at night.
I have been able some-
times to read a book by this light, when sailing in the
Bay of Bengal, and the South Atlantic Ocean. Ani-
mals of the tribe now under notice, are perhaps more
remarkable than any others for this power of giving
light; so you perceive that they are endowed with facul-
ties capable of yielding both pleasure and pain, even to
proud man himself. Yet if you draw one of these
animals from the water, and lay it in the sunshine, it
resembles a mere mass of jelly, in which you cannot
readily detect any organs, and, in a little while, the
w^hole mass seems to melt with the heat, and flows away
like water, — leaving so little solid matter behind, that;
when dry, this can scarcely be detected.

53. That the Medusae are really animals, there can
be no doubt, for they swim with a regular slow motion,
seizing upon small fish, crabs, and other minute beings,
by means of their stinging tendrils (52.) By contracting
these long appendages, they contrive to throw their food
into a cavity which serves them as a stomach. When
you cut off a part of the body of a Medusa, the piece
will often continue to swim, though we know not at

Medusa.

THE HYDRA THE SIMPLEST OF ANIMALS. 47

present whether it be capable of forming a new and per-
fect animal — as in the case of the earth-worm (43).

54. It appears, then, that among the least perfect of
living things, not only the solids, but even the fluids, are
more simple in their structure, or less distinctly organ-
ized, than they are among beings of more dignified
station. And indeed this seems perfectly reasonable.
The fluids are designed to furnish the materials for the
growth of the sohd parts, — and, therefore, when the
solids are nearly or exactly alike in all parts of the
body, it is obvious that much less variety of matter is
requisite in the fluids.

55. It is also obvious, that when the frame of an
animal contains very little solid substance ; as in the
Medusae ; the fluids may be in a larger proportion and
more watery.

56. It will now less astonish you that the powers of
life are more equally distributed through the whole frame
of the simple creatures that form the lowest links in the
chain of animate nature ; and that portions of a certain
size cut from their bodies should be so often capable of
preserving th^ir life, independently, so as to constitute
distinct beings ; for each portion possesses a part of
every thing necessary to form the entire animal; which
cannot be the case in those which are composed of many
distinct systems of organs (24).

57. In fig. 3, you see a magnified repre-
sentation of what is, perhaps, the simplest of
all animals. It is called the hydra viridis
by naturahsts. It inhabits fresh waters,
usually climbing on the under surface of
the leaves of aquatic plants, and is so
small that close attention is necessary to
enable us to detect it with the naked
eye. You observe that the body of this ^^
animal is shaped somewhat like a jug Hydra viridis.
placed upside down, and adhering by its

base to the surface from which it depends. What cor-
responds to the mouth of the jug is surrounded by long
and flexible arms, by means of which it seizes its prey

48 VITAL FUNCTIONS OF THE HYDRA.

The body is hollow, and the cavity communicates with
the arms, which are somewhat tubular, and the whole
of this internal space may be considered as the stomach
of the hydra. The food, which it swallows with great
voracity, passes freely from the body into the arms and
back again while undergoing the process of digestion ;
and this motion depends upon the power possessed by
all parts of the animal to contract or expand themselves
at will, so as to press the contents of the general cavity
from place to place.

58. As it is evident that the stomach and bowels of an
animal answer the same purpose in their economy that
the roots do in the case of plants — namely, to select and
absorb the proper nourishment for the Uving body — there
is every reason to suppose that the whole interior sur-
face of the hydra, including even the arms, has the
power of changing the food into nourishment — a process
that is called by ph3^siologists digestion — which may be
regarded as the first step towards assimilation (47).

59. There is also every reason to suppose that the
nourishment, when formed, is taken into the substance
of the hydra by all parts of this surface ; or, in other
words, that the sides of the cavity have every where the
power of ahsoiyiion ; for not even the most delicate mi-
croscopes can detect any distinct passage by which the
nourishment can enter, or any particular reservoir or
canal, in the solid frame of the animal, for the reception
or distribution of this matter.

60. You now perceive how wisely it is ordered that
the food should be thrust backward and forward from
the body to the arms, and from the arms to the body,
so that every part of the animal may absorb the nou-
rishment necessary for its growth and sustenance. For
the hydra has not the blood-vessels, which in the more
complex animals, receive the nutritive fluid, and convey
it to all parts of the body, — and it is, therefore, neces-
sary that the only great cavity should fulfil, in some
degree, the double purpose of a stomach and a heart.

61. If we turn a hydra inside out, like the finger of a
glove, strange as it may seem, the creature does not die.

VITAL FUNCTIONS OF THE HYDRA. 49

What was the external surface becomes a stomach, and
what was the stomach becomes an external surf ace. Yet
the animal continues to grow and prosper ; proving that
not only the inner, but the outer surface also is capable
of digesting food and absorbing the nutritious fluid which
supports the animal.

62. From what has been said of the hydra, you will
naturally conclude that its organization must be ex-
tremely simple, and hence, that all parts of the animal
must possess powers of life nearly equal, both in degree
and kind (44) ; so that when divided into many parts by
the knife, each part may live separately, and form itself
into a perfect animal (43). This is the case to an extent
so remarkable, that if the hydra be split throughout a
great part of its length, each part forms a distinct animal,
adhering to the remains of the original body. If the same
operation be performed upon each of these branches,
thus artificially produced, two more animals will be con-
structed in the same manner ; and we know not how far
the process might be carried before the Hfe of the hydra
would be destroyed. In fig. 4, you see a single speci-
men which has been split repeatedly in this manner,
until it has formed seven hydras attached to the original
body, and having a cavity or stomach common to
them all.

63. Sometimes the hydra splits itself Fig. 4.
spontaneously into halves, each of
which becomes an independent ani-
mal.

64. If we cut one of these simple
creatures into a number of pieces in
any direction, each piece will be found,
in many cases, to complete itself and
form a perfect hydra ; but even here there is a limit to
the powers of life. If the division be carried too far, or
if the animal be crushed, the fragments die. We cannot
powder a hydra, like a piece of hme, and yet leave
every particle a hydra ; because every thing that has
life is organized, and if we destroy any essential part of
its organization, it must cease to live.

50 HYDRA FORMED OF CELLULAR TISSUE.

65. In attempting to discover the real organization of
the hydra, we perceive little in its substance but a mass
of soft and flexible membranes formed into cells con-
taining an animal juice, which simple fluid answers the
purpose of blood, and supports the frame. The cells are
so small that we cannot distinguish them by means of
sight, but w^e infer that they exist, because the fluid does
not run out, at once, when we cut the hydra open, and
then subject it to light pressure. This membrane appears
to be more firm in some places than in others, probably
because it is thicker, and perhaps because the cells are
smaller in such situations. The external surface of the
animal, which we may call the skin, has more firmness
than the internal parts, but with this exception, there is
nothing to distinguish one portion of the body or arms
from another, and it is, therefore, not so very wonderful
that small pieces, when cut oflf from the parent animal,
should continue to live.

6G. I must now give you two more definitions, in
order to prevent the necessity of too many words in our
future descriptions. The membrane of which I have
been speaking is called cellular membrane ; something
analogous to it is found in the structure of every thing
possessed of life.

67. In animals, the cells of this membrane are seldom
perfect, but have communications with each other, per-
mitting the fluids which they contain to flow slowly
from one to another ; and, in particular parts of the more
perfect animals, these openings are so large and nume-
rous, that the membrane seems to be composed of a net-
w^ork of irregular fibres, rather than a collection of cells.
For this reason, and some others which need not be
mentioned here, the membrane is often termed by phy-
siologists the cellular tissue. It is important that you
should remember that both the terms just defined are
often employed, indiscriminately, with the same meaning.

68. The cellular membrane that appears to form the
whole body of the hydra, is found in all animals in great
abundance, but is diflferently arranged according to the
particular class of animals in which it is observed. In

JTATURE OF CELLUr^AR TISSUE.

man, if we examine a single film of this tissue, under a
strong microscope, we find that even the sides of the cells
are evidently composed of very minute fibres, with in-
tervals between them too small to allow the most search-
ing liquid to flow readily through the tissue, but large
enough to make it less wonderful that this membrane
should be found capable of absorbing nourishment, and
that it should slowly transmit fluids in the form of vapour,
as, in the sequel, you will find that it does. The fibrous
appearance just described, is well displayed in fig. 5,

Fig. 5.

Cellular membrane magnified.

which represents a film of cellular tissue, highly magni-
fied. On increasing the power of the microscope still
further, the fibres seem to be composed of rows of glo-
bules : but all observations made with instruments of
such prodigious power, are very apt to produce decep-
tive appearances. Those of you who have ever seen
an animal skinned, may have noticed that the skin is
attached to the body by a white or transparent sub-
stance, which may be torn very easily in many places,
but, in other situations, it requires to be cut before the
skin can be detached. This is the cellular membrane
or cellular tissue.

69. To show that the cells communicate with each
other, it is only necessary to mention that dishonest peo-

52 NATURE OP CELLULAR TISSUE.

pie, when preparing chickens or other small animals for
market, not unfrequently introduce a small pipe through
the skin, and blow through it into the membrane beneath.
The air enters the cells, and passing from one to another
all over the body, gives it the appearance of being very
fat, and ignorant purchasers are not always able to de-
tect the deception.

70. It sometimes happens that, when a man has
broken one of his ribs, the air from the lungs is forced
into this loose cellular tissue through a wound made by
a portion of the broken bone. The body may then be
swelled by the air until even the neck disappears, and
the person resembles a great bladder, with nothing but
some features of the face, the palms of the hands, and
soles of the feet retaining their natural appearance;
Yet this accident, frightful as it looks, is not necessarily
dangerous. The air may be rapidly absorbed, or it may
be allowed to escape through a few small incisions made
in the skin by the surgeon.

71. In many parts of the larger animals we find col-
lections of fat in the cellular tissue ; and anatomists have
discovered that fat is always collected into masses
which, when examined carefully, resemble little bags or
sacs of oily matter, bound together by the cellular mem-
brane that surrounds them. When one of these sacs is
examined under the microscope, it is found to contain a
multitude of very minute hollow globules, composed of
a transparent membrane, and grouped together much
like a bunch of grapes. Each of these globules contains
an exceedingly small drop of the oily matter that gives
character to fat, so that in rendering lard or tallow, or
in other words, melting it in boiling water, the oil bursts
the globules, and rises to the surface of the water. With-
out the aid of heat or strong pressure, the oil cannot
escape. Now we are unable to discover any communi-
cation between these globules, such as is found between
the cells of the common cellular tissue ; and hence,
modern physiologists have generally believed these
bundles of globules to be formed of a peculiar mem-

NATURE OF ADIPOSE TISSUE. 53

brane which they term the adipose tissue. But cellular
membrane in many places is found to be
impervious to air or any other substance
which we attempt to introduce artificially;
as I shall have occasion to mention here-
after ; and we have not yet discovered any
material difference in other respects between
the latter and the adipose tissue. It is quite
as consistent with the probable truth, to re-
gard the globules containing the oily matter
of fat as closed or complete cells of cellular
membrane. The appearance of adipose tis-
sue, so called, is seen in fig. 6. Adipose Tissue.

72. Of cellular tissue, then, the whole body of the
hydra is composed, though, from its granular appear-
ance, it probably contains something analogous to fat in
various parts of its substance. It seems to possess no
particular organs, properly so called, for although the
skin is a little firmer than the other parts, yet its sub-
stance is apparently precisely the same, and although
the arms of the animal are used for seizing its prey, yet
when one of them is cut off, it almost immediately
becomes a perfect animal ; and it is most curious to
observe how fully a creature so extremely simple can
perform the different functions w^hich, in more complex
beings, require as many different systems of organs for
their accomplishment.

73. As there is no difference between its inner and
outer surface (61), it is obvious that it can carry on
digestion (5S) and absorption (59) by means of its skin.

74. As the hydra dies, hke all other animals, when
entirely deprived of air, and as it has no particular
organ, like those of a fish or any other aquatic animal,
for breathing the air-bubbles combined with the w-ater
in which it is suspended, it is obvious that it breathes by
its skin.

75. It owes its form entirely to the elasticity of the
cellular membrane, and it can only change that form
by contracting one portion of the membrane while it
allows another to remain relaxed. Yet it walks slowly

54 CONSCIOUSNESS IN THE HYDRA.

along the stem or the leaf of a plant, by arching its
body and applying its mouth and tail alternately to the
surface.

76. The involuntary motions that drive the food from
the stomach into the arms, and back again (57), and
agitate the nutritive fluid or blood, from cell to cell,
throughout its substance, so as to nourish every part of
its frame without the aid of blood-vessels, are not its
most remarkable functions ; for it shrinks when touched
or disturbed; so as to give plain evidences of conscious-
ness, although no human skill can detect the slightest
trace of a nerve in its organization.

77. Without any visible muscles, it can wrap its long
arms around an active little insect or worm ; and so
voracious is it, that when two hydrse happen to seize
upon opposite ends of the same prey, each swallows his
own portion, until their mouths come together ; when the
larger of the two has been known not only to gorge the
whole of the prey, but with it the body of his antagonist
also. The result of the contest forms a curious excep-
tion to the truth of the old adage, that „.

*^the weakest goes to the wall ;" for it so ^^'

happens that the smaller hydra, while
in the stomach of the larger one, lei-
surely devours and digests the whole
of the prey, but being himself rather
indigestible, he is ultimately ejected,
the happier for having lost the battle.
Fig. 7. represents a contest of this kind. ''""'"^ '' "^''^"'

78. You have now obtained a tolerably clear idea of
the difference between organized beings and inorganic
matter; and you have also a clear conception of the
simplest organization which is consistent with animal
life. In the order usually observed by writers on phy-
siology, I should now proceed to point out the distinc-
tions between animals and vegetables. But if we begin
with the beginning of these two scales of living things,
as we should do when teaching the first principles of
the science, the establishment of a clear distinction is
by no means an easy undertaking. The simplest forms

ORGANIZATION OF SIMPLE ANIMALS. 55

of vegetable and animal life resemble each other so very
nearly, that no perfectly satisfactory definition of the
difference has ever been given ; and even between a
forest tree and the bird that builds in its branches or
the squirrel that subsists upon its nuts, there are more
points of resemblance, so far as the vital functions are
concerned, than you would be able to comprehend, were
I to attempt to explain them at present. For my own
part, being unable to discover any positively certain
distinction between the two great kingdoms of animated
nature in the peculiarities of their organization, I have
arrived at the conclusion that consciousness and will —
faculties that appear to be exclusively possessed by ani-
mals— form the only marks which can, in every case,
distinguish them from vegetables, and these being func-
tions of the mind, are beyond the reach of physiology,
which treats only of those of the organization (39, and
note).

CHAPTER lit.

ON THE ORGANIZATION AND FUNCTIONS OF ANIMALS SO SIM-
PLE AS TO BE APPARENTLY DIVESTED OF SPECIAL ORGANS.

79. In the last chapter you learned that an animal
may exist with a frame so simple that we can detect
nothing in its structure but simple cellular tissue, and
yet may seek, catch, and digest its food, grow, fee],
and execute its will, without the aid of any particular
organs. But it must be evident to you that such soft
and deUcate beings are altogether unable to protect
themselves against powerful enemies, unless they escape
observation by their minuteness. Most of these crea-
tures are therefore exceedingly small.

80. The very weight of their own bodies would pre-
vent them from easily preserving their shape and per-

STRUCTURE AND HABITS OF POLYPI.

Fig, 8.

forming their necessary functions in a fluid as light as
air ; and they are therefore seen to inhabit the water
only.

81. Some of the smallest known animals are destined
by nature to remain fixed in one spot from near the time
of their birth. These cannot go in search of their prey,
and would therefore starve if nature had furnished them
with no means of bringing their prey within their reach.
At fig. 8. you see a specimen of a polypus ; but not the
somewhat dangerous marine animal of that name, of
which are told so many wonderful stories, either true
or fabulous, and which is more properly called the
cuttle-fish. This little animal

belongs to the same general
class of minute beings with
the hydra viridis, (fig. 3,) and
that which forms and inhabits
the various kinds of coral.
The particular species here
represented is a zoanthus.
It is permanently adherent to
the rock on which it grows ;
and though it can elongate
and contract its body, and
employ its numerous arms, or
tentacula, as they are called,
like the hydra, yet it would
be difficult for it to obtain
food without some other con-
trivance for bringing its prey
within its reach.

82. This is efiected, in nearly all the polypi, by cer-
tain little fibres, like hairs, placed in various orders
around the mouth. These hair-like organs, which are
called cilia, are continually in motion during life, and
produce currents in the water, sweeping towards the
mouth of the animal ; so as to bring any particle of food
which may happen to float near the polypus, within
reach of its tentaculae.

Zoanthus.

PREHENSION AND CILIARY MOVEMENT

83. The cilia of the polypi are so minute, that they
are altogether invisible to the naked eye ; but in fig. 9
you see a highly magnified vievi^ of the cells of the
flustra carhacea, a very minute species of coral, that
grows on the surface of marine stones, shells, or plants.

Fig, 11.

Fig, 9.

Fig. 10.

Cells of a Flustra.

Plustra Magnified.

Cilia of Flustra.

Fig. 10 represents one of the animals greatly enlarged,
and you observe the arrangement of its numerous
tentacula around the mouth. In fig. 11 you have a
single tentaculum, separately magnified, showing the
cilia ranged in a row along its sides, and the arrows
marking the direction of the currents of water produced
by their perpetual vibration.

84. In those polypi which are not Fig. 12.

fixed permanently to one spot, the
cilia become organs of locomotion,
and instead of moving the water
toward the animal, they move the
animal toward the water. In fig. 12
I present you with the likeness of a
little microscopic animal, generally
considered as a polypus, but it has
cilia only, without tentacula. Its
body is a bell, placed on a long foot
stock, that is contracted or elongated
at pleasure bv the animal ; and by the vortieeiia.

68 CILIARY MOVEMENT CONTRACTILITY.

base of this foot-stalk it adheres to any surface, when it
chooses to do so. When attached, this animal — the
vorticella cyathina of naturalists — pursues its prey by
suddenly elongating its pedicle, a, but instantly retreats
when in danger. When detached, the cilia, h, cause it
to move and whirl through the water in a most curious
manner.

85. We know very well how the motion of the bodies,
foot stalks, and tentacula of poylpi may be produced
by the contractile power of the cellular tissue of which
they are composed. For this contractility, as it is techni-
cally called by physiologists, may shorten any one part,
or render it smaller, by forcing the fluids from the cells
of that part into those of any other portion of the body
or its appendages ; which will, necessarily, render these
latter larger or longer. But we can form no idea of
the cause that produces the constant motion of the cilia.
We have every reason to believe that this motion is not
muscular, like that which effects locomotion in more
complex animals ; for, when a piece of the animal on
which several cilia are based is cut ofl' from the body,
the cilia continue in action unchecked while lii'e remains,
and keep the fragment in motion, as though it were a
distinct animal.

86. Even in aquatic beings of much more complex
structure than the polypi, — beings that have a heart,
blood-vessels, breathing organs, muscles for voluntary
motion, nerves, &c. — we still find cilia, apparently moving
in the same manner, and capable of carrying fragments
about when detached from the body ; though in these
animals the cilia are not designed to supply food, and
are usually placed about the breathing organs instead of
the mouth. The common fresh water muscle displays
a beautiful arrangement of this kind on the edges of its
breathing organs, — where it keeps the water constantly
in motion, for purposes which you will understand here-
after.

CIRCULATION IN PLANTS. 59

87. Even among plants, the Fig, 13.

existence of something of the
same kind is inferred. Fig. 13
represents a single joint of a pe-
culiar water plant, like a grass,
called by botanists the char a his-
pida, in great degree deprived of
its bark, so as to allow the ob-
server to perceive, under the mi-
croscope, the singular circulation
of the sap, which is continually
going on in the hollow of each
joint of the transparent stem. In
fig. 14, you see a portion of a
joint highly magnified ; the cur-
rent of sap in the cavity is per-
petually passing downward on
one side of the stem, and upwards
on the other side. The white
line marks an intermediate space
between opposing currents, wliere
the sap remains nearly at rest.
Now you observe a great many
regular and somewhat spiral lines
of little globules in this figure.
These are small green bodies,
seemingly connected together by
long spiral fibres, such as are
often found in the inner surface
of the cells of vegetables. These
fibres pursue the same direction
with the current of the circu-
lating sap, and if any one of them
be broken, it instantly twists it-
self about in the middle of the branches shooting from the ends

*. u„ ii ri „ „ +U" r ^'^^ ?> „ j of each joint, c, The stem with

tube, "like a thmg Oi lite," and the outer bark removed, and pre

arrests the circulation. If

single globule happens to become

detached, it immediately whirls round and conducts

itself much in the same manner with those minute ani-

Stem of the Chara.
a. The outside bark, b, b. The

Q pared for seeing the circulation.
d, d, The outer bark of the plant.

CIRCULATION IN PLANTS.

Fig. 14.

A portion of the stem of the Chara, highly magnified.

mals that are furnished with ciHa (84), and we have
every reason to believe that the cause of naotion is the
same in both. The larger rings in the figure represent
moats floating with the sap.

88. The polypi not only resemble plants in their ex-
ternal appearance, after the manner of the zoanthus or
animal flower (81), but they even multiply by buds, like
a tree. These buds are called gemmules. They soon
fall ofl^, and commence an independent existence. They
are provided, from the first, with moving cilia, which
carry them oflT in search of a proper place of perma-
nent residence, the moment they are detached from the
parent. In fig. 15, you see a figure of the gemmule of
a flustra, covered with its cilia. Even those

polypi which remain fixed for life in one spot,
have thus the power of transporting their race
to a distance, by means of a locomotive power
which the young lose for ever the moment that
they select their station: but they make this
selection voluntarily and with judgment, though
the motion of the cilia is constant, and seem-
ingly involuntary in many of them.

89. By far the majority of the various kinds of polypi
live together in extensive societies, of which the num-
bers defy calculation. The difl^erent members of each
group remain connected together, in such a manner
that the whole community forms one living mass, and
each polypus, instead of being a distinct and separate
animal, resembles one of the divisions of the original
hydra represented at fig, 4 (62).

SOLID SUPPORTS OF THE POLYPI.

90. Now such vast communities composed of such
soft materials, could not possibly preserve themselves
from destruction without some solid support. Provi-
dence has, therefore, bestowed upon them the power to
form for themselves cells or stems of lime or horny mat-
ter, in which their soft flesh may be encased, or over
which it may be spread.

91. Sometimes this support is a
jointed tube, branching beautifully like
a tree, with openings in the side of
each joint, through which the mouth
and tentacula of a polypus peep forth,
and expand themselves like a flower ; as
in the sertularia. Fig. 16.

92. Sometimes the support consists
of round cells placed side by side, like
the barrels of an organ ; as you see in
the tubipora, a kind of coral. Fig. 17.

93. When the flesh of the commu-
nity is spread over the surface, instead of being enclosed
within the support, the bodies of the individual polypi
are often enclosed in cells formed in the flesh, from

Sertularia.

Fig. 17.

Tubipora.

Fig, 18.

Precious Coral.
a, A portion of the stem with its poly-
pi, of the natural size, b, A magnified
portion of the stem with its fleshy cover-
ing and polypi, c, A portion of the fluted
solid axis with the fleshy matter re-
moved.

which cells they project themselves in search of food.
The solid axis often bears the strongest resemblance to
a plant with leaves or flowers. Sometimes it is com-

62 SECRETION.

posed chiefly of lime ; as in the common or precious red
coral, fig. 18, where a represents a stem of the natural
size, h, a portion with three of the polypi, one contracted,
the other two expanded, and the whole highly magnified.
In other species the axis is horny ; as in the gorgonia—
fig. 19, which represents a portion of the gorgonia bri-
arius with a section of the flesh, show-
ing the axis, the cells, and some of the Fig. 19.
individual polypi within them, also great-
ly magnified.

94. In many kinds of coral, called
madrepores, the solid support of the
community of polypi is as massive and
almost as firm as a limestone rock,
and the hard cells merely indent the
surface of the rock, which continues
growing with rapidity; the old cells be- Gorgonia magnified,
ing obliterated and new ones formed as

one generation of these little architects succeeds another.

95. You have heard, no doubt, that in tropical seas
the coral rocks grow with such rapidity that vessels
are frequently wrecked upon them, where a few years
before the soundings were very deep ; and that new
islands are continually appearing where once the largest
vessels might navigate in safety. Yet all this growth of
seeming rock is produced by an exudation from the
bodies of countless millions of little animals, composed
nearly, if not entirely, of simple cellular membrane,
without any distinct organs except the cilia, of the true
nature of which we as yet know nothing.

90. You may now be able to comprehend what is
meant by secretion — a term applied by physiologists to
that process by which a living body separates from the
fluids which nourish it any substance which is required
for a definite use, or which it is desirable to remove
from the body. The rocky base or branching stems of
corals and gorgonia are secretions from the substance
of the polypus, as the outer skin or cuticle of a man —
that which we see raised by a blister — is secreted by
the surface of the membrane beneath it. If the cuticle be
rubbed off a man's hand, a new one is almost imme-

NUTRITION. 68

diately formed, and if the hard cell of a polypus be
broken, it is rapidly repaired. The power of secreting
lime or horny matter is not confined to the surface of
the polypus, but is as general as its other functions ; for
we often find grains of the same material scattered
through the substance of the flesh.

97. This power is one inherent in animal cellular
tissue, the material of which the true skin and much of
the solid bulk of all animals is composed. Finding it
thus exemplified on the very confines of animal life, we
are less surprised at its effects in more complicated
beings, where we observe it clothing the shell-fish with
their thousand elegant coverings, the insects with hard
and jointed shells serving them as a kind of external
skeleton, the reptiles with scales that are sometimes
used as a house to live in (tortoises), and sometimes in
place of feet for crawling (snakes).

98. The hair, claws, horns, nails, teeth, &c., of the
more perfect animals and man, are all produced by the
action of a similar power, and consist of horny or cal-
careous matter, according to the purpose for which they
are designed. As if to prove that all parts of the body
are capable of forming substances of this nature, the
history of disease furnishes us with many examples of
the irregular deposit of bony or horny matter, in the
substance of all the organs of the human body. The
most common affections of this character are called
ossifications, and these have been found in the muscles,
the blood-vessels, the heart, liver, brain, &c. Some-
times large incrustations of bone have been formed on
the surface of the skin, where they have grown and fallen
off, time after time, without producing any sore, or
leaving any mark behind them.

99. As you advance in the study of physiology, you
will discover that, as the complexity of the organization
of animals increases, the number of secretions, or mat-
ters separated from the general mass of the fluids, be-
comes greater and greater, until it almost defies calcu-
lation. Very many of these substances are deposited in
the interior of the animals, to form and support the
several different organs ; as the bones, the muscles, the

64 CONTRACTILITY.

brain, &c. The secretion of such substances is termed
nutrition.

100. Another class of secretions, more commonly so
called, which we see in the higher orders of animals,
are of a fluid character, and are designed, not to assist
in the formation or growth of the frame, but to answer
some useful purpose in the performance of the vital
functions. The bile, for instance, seems to be a natural
purgative secreted by the liver ; and the tears, which are
secreted by two little organs situated within the orbits
of the eyes, are intended to prevent them from being
injured by the friction of the eyelids.

101. The functions of assimilation (47, 48), nutrition
(99), and secretion (96), — or, in other words, those which
are connected with the growth and sustenance of the
frame of a living being, — are common to all organized
beings, whether plants or animals ; and have been called
the functions of organic life, to distinguish them from
sensation and voluntary motion, which, being peculiar
to animals, have been termed the functions of animal life.

102. I will close the present chapter with some defi-
nitions and illustrations of a few terms which it is
necessary that you should understand before we enter
upon the study of the organization of more complex
animals ; a study that I hope will prove more entertain-
ing than these preliminary but indispensable remarks.

103. You have been told that the power by which the
cellular tissue that forms the bodies of polypi forces its
fluids from cell to cell, so as to change its form and
enable it to move its arms, &c., is called by physiolo-
gists contractility (85). The same power is employed
in pushing tlie fluids or blood from place to place,
in order to nourish all parts of the frame (32). This
motion is so gentle and slow, however, in the minute
beings of which we have been speaking, that it cannot
be perceived by the eye.

104. Now this contractility is a peculiar property of
living things, and differs entirely from that power of
contraction often observed, in consequence of cohesive
attraction, in things which have not life. It has nothing
in common with the cause that makes a globule of

CONTRACTILITV.

quicksilver assume a rounded form when laid upon

a china plate, or draws back and shortens a piece of

molasses candy, after being stretched. It displays itself

in plants as well as animals, — in every thing that is

organized (20) — and is therefore

a property or function of organic Fig, 20.

life (101).

105. In plants, this contracti-
lity rarely produces very sud-
den and obvious motions, though
there can be no doubt that it is
interested in moving the sap, as
it moves the fluids of a polypus.
In the sensitive plant, however,
in the hedysarum gyrans, —
a shrub that keeps its branches
continually rising and falling
almost with the regularity of
the pendulum, — and in the tube
of the chara hispida (87), we see
much more striking resuhs of
this property. But even these
remarkable examples are trifling
in comparison w^th many that we
observe in the animal kingdom.
In illustration of this fact I will
give you a description of the
Portuguese man-of-war, a most
beautiful marine animal called
by naturalists a physalia. Fig.
20.

106. This little creature some-
what resembles one or more
groups of hydrge deprived of
their arms, d, d, and suspended
from the under surface of a
large bladder, a, composed of
very transparent cellular mem-
brane and distended with air.
This bladder is called the body Physaiia Megaiista.

CONTRACTILITY.

of the animal. At one extremity, it is occasionally
curved so elegantly as to resemble the neck of a swan.
It floats upon the surface of the sea and is surmounted
by a membranous sail, which, as you see in the figure,
is full of cavities, ranged side by side, like the fingers
of a glove, h. From the middle of each group of jug-
shaped appendages, d, d, which seem to be so many sepa-
rate stomachs, you may observe a number of slender
organs depending, by which the physalia seizes its prey.
The sailors call the largest of these, c, c, the cable, and
naturalists term them tentacula — a name given to a great
variety of organs designed for a similar purpose in the
lower orders of animals (81). When fully extended, in a
physalia six inches long, this cable may measure five or
six yards. The upper part of the sail is of the most
splendid carmine colour; the back of the bladder, of
ultramarine blue ; the intermediate space is shaded ele-
gantly through every tint of purple, and the whole sur-
face is iridescent in oblique lights. When you recollect
that the substance of the animal on which nature has
impressed such glorious hues is more transparent than
the palest amber, you will be able to form some con-
ception of the exquisite beauty of the little being that
looks so humble in the figure ; — a beauty that I could
as readily describe, as a painter could reduce to can-
vass the ever-changing features of a sunset sky.

107. The colour of the groups
of stomachs is blue, and the cables,
or tentacula, are generally of the
same hue ; but sometimes they aie
carmine. In fig. 21 you have a
plan of a portion of the cable, very
highly magnified, and at a you
observe that the general form of
the organ is cylindrical. It is
studded with numerous little bead-
like bodies ranged round it in
a spiral line, and each of these
beads is covered with minute and
hard spines, of which we know not
the nature. One of them is repre-

Ciibh- of Phvsalia.

CONTRACTILITY.

sented at h. Their spines are so sharp as to enter the
hardest wood ; and when the cable accidentally touches
the wood work of the vessel, as the naturalist lifts the
animal over the rail in the little gauze dip-net used for
catching it, the cable is generally broken before it can
be detached. The moment that a small fish, crab, or other
marine animal comes in contact with the organ, it is dis-
abled by the wounds received from the prickles, which
are supposed to infuse a poison. The pain induced when
the cable touches the skin of a man is very severe, and
lasts sometimes for twenty-four hours, though it has been
much exaggerated by travellers. The medusae (fig. 2),
and many other soft or gelatinous marine creatures, have
similar organs. It is not improbable that the prickles
are hollow, and seated upon poison sacs, like the veno-
mous teeth of the rattlesnake, and the spines of nettles.

108. Now, when the physalia wishes to spread its sail,
it excites the contractility of the air sac, and forces the
air into the finger-like cavities already noticed. Then,
by using one end of its body as a kind of rudder, it can
sail not only before the wind, but obliquely, in the man-
ner that seamen term sailing on a loind.

109. The moment the prickles on the cable have
secured any prey, the organ contracts so strongly that
it measures scarcely more than as many inches as it pre-
viously measured yards. The little beads are brought
into contact with each other (fig. 21, a), and the prey lies
within reach of the bottle-shaped stomachs, by one or
other of which it is swallowed. This is perhaps the
most remarkable instance of vital contractility with
which nature presents us.

110. It will be evident to you, on a little reflection,
that this vital contractility, which produces either per-
ceptible or imperceptible motions in various parts of the
animal frame, is not necessarily dependent upon con-
sciousness and will. For no one dreams that a plant
can feel the sap flowing through it, any more than a
man can feel the blood circulating through his veins :
nor is it more difficult to believe that without sensation,
the cable of the Portuguese man-of-war may contract the
moment that it strikes its prey, than it is to comprehend

68 CONTRACTILITY STIMULANTS.

how a whole branch of a sensitive plant should shrink
the instant that we rudely touch one of its leaves, though
it will not do so when shaken by the breeze. If, then,
i have said that even the simplest animals seem to give
evidence of will in many of their motions (17), it is not
because their frame or their organs possess such powers
of contraction as have been described, but because they
all perform occasional motions hke those of the hydra
in walking, which are obviously voluntary.

111. Now almost every part of the most perfect ani-
mals, including man, displays contractihty of some kind ;
and yet but few of these parts are gifted with feeling,
and very many of their motions are altogether indepen-
dent of the will.

112. Contractility, then, is a power resident in all
organized bodies ; but it produces no motion until it is
excited by some internal or external cause. In the case
of the cable of the Portuguese man-of-war, we see it
excited by the contact of a fish or some other small
animal; and here the cause is sufficiently obvious.
When the air bladder of this little creature contracts in
order to expand the sail (108), the organ is obviously
excited by the ivill ; and here the cause is much more
obscure. The stomach of the polypus, like that of more
perfect animals, is excited into action by the food ; and
the direction of the motion is determined sometimes by
the quality of the food, and sometimes by the changes
which it has undergone during digestion. Hence, it
drives the nourishment from its general cavity into the
arms and back again, and also ejects altogether any
injurious or indigestible matter that may have been
swallowed accidentally ; as when its voracity has in-
duced it to swallow another polypus (77).

113. Any cause which excites a part to contract is
called a stimulant to that part. Thus, in man, the will,
through the medium of certain nerves, stimulates the
voluntary muscles, one after another, so as to cause
him to walk or strike a blow. The flow of blood into
the heart stimulates that organ, and causes it to urge
forward the circulation.

114. There is a kind of contractility observable in all

TONE — TONICITY. 69

living bodies, which is always excited while life remains,
though it acts more powerfully at certain times and in
certain conditions of the body. I mean that power
which causes all parts to compress their contents with
a certain degree of firmness. If it were not for this
kind of contractility, the polypi and other soft animals
could not preserve their forms ; for a simple cellular
membrane, capable of being greatly stretched by disten-
tion, and filled with nothing but fluids, could have no
stability if it did not at all times press upon its contents.
That it does so in all animals is easily proved, but I will
present you with only a few examples drawn from the
natural history of man.

115. If you pull your finger with some force, as
though you designed to draw it from the hand, you
perceive that you can very readily separate the surfaces
of the bones at the joints to a certain distance ; but the
moment you let go your hold, the finger is drawn back,
even against your will. This shows that the muscles
are always in such a state of active contraction. The
same thing is seen in the face; for however it may be
distorted by passion, when the mind becomes calm the
habitual expression returns without any effort of the
will. This kind of contractility is called tonicity^ and
the force with which it contracts is called its tone.

116. You cannot separate the surfaces of a large
joint, like the shoulder, without using considerable exer-
tion; because the powerful tone of the large muscles
which surround it draws the bones together with great
force. But sometimes an accident, such as a severe
blow or an attack of palsy, destroys the tone of these
muscles ; and then the mere weight of the arm will
sometimes draw the head of the shoulder-bone entirely
away from its socket. You all know how different is
the expression of the limbs and face of a sleeping or
fainting person, and that of the same individual when at
rest, but awake. This difference results from the fact
that, during the fainting and sleeping conditions the
tonicity of all animal bodies is much diminished.

117. The same evidences of tonicity are observed in
the skin, though in a much less marked degree. Cold

70 TONICITY.

weather increases the tone of the skin, while heat
diminishes it ; hence we see that all parts of the body
look comparatively firm in winter and relaxed in
summer.

118. In young persons who have been rendered thin
by severe illness, the skin seems relaxed, and hangs
loosely over certain parts of the body ; but when the
health improves, the skin contracts so rapidly that long
before the patient has " recovered his flesh," as we
commonly hut not very 'proj)erly say, it appears as firm
and as tight as ever. This is an evidence of tonic con-
traction, tone, or tonicity, and you will find, as you ad-
vance in this little volume, that tonic contraction plays a
very important part in the economy of health. Were it
not for this kind of contraction in the half-emptied blood-
vessels, a person who had once fainted would never
recover ; for the heart cannot carry on the circulation
of the blood in vessels that no longer contract upon
their contents (113). I introduce this illustration to
show that the subjects on which we are now conversing
are not so unimportant to man and his interests as they
may at first appear to you. The power of the heart
and the nature of the circulation you will understand
much better hereafter.

119. Whether the several forms of contractility which
have been described may not all be the result of the
same general cause, is, perhaps, doubtful; but by many
physiologists they have been regarded as distinct pro-
perties. There are also other forms of contractility
displayed by the muscles; but these you are not yet
prepared to comprehend.

120. Having now given you some idea of the struc-
ture of the simplest animals, the manner in which they
are supplied with the materials necessary for their
growth and support by digestion, the mode in which
they often supply themselves with a solid support by
secretion, and the nature of the vital forces by means of
which they preserve their form, move from place to
place, seize their prey, and urge the nutritive fluids
throughout their structure so as to nourish all parts of
their frame, it is time to close this chapter.

CHAPTER IV.

ON THE NECESSITY FOR MASTICATORY AND DIGESTIVE
APPARATUS IN COMPLEX ANIMALS.

121. Most of the animals of which we have been
speaking are so extremely simple, and at the same time
SO minute, that they require but slender protection, and
hardly stand in need of any distinct organs for the per-
formance of their proper functions. A single cavity,
lined by what seems to be merely a continuation of their
skin, suffices to receive and digest their food. All parts
of their bodies lie so near this cavity that each portion is
nourished by absorbing the digested fluids directly from
the stomach. It does not appear that any particular
organ of taste or smell is required to enable them to
distinguish what food is proper or injurious for them,
but they take what the beneficence of Providence sends
them, without asking questions. They do not chew
their food, and hence require no solid parts like teeth or
jaws. We shall soon perceive, however, that much
more complex apparatus is employed by animals a Httle
more elevated in the scale of creation.

122. In many of the medusae (52) the thickness and
bulk of the body or cap of the animal is so great that
it cannot be conveniently nourished by absorption from
a simple central cavity ; and in these animals we find
the .cavity which answers the purpose of a stomach
divided into four principal sacs in the forai of a cross,
the corners of which are extended into tubes that pene-
trate the substance of the body, ramifying continually
as they go, the smaller branches opening into each
other, so as to form at last a complete net- work of canals,

MASTICATORS APPARATUS.

through which the sea-water, to- Fig. 22.

gether with the digested food

which it contains, may be driven

about from place to place for the

support of all parts of the frame.

In fig. 22 you see a portion of the

edge of the medusa represented

at fig. 2. The irregular white lines

represent the ramifications of the

stomach. Edge of Medusa.

123. You have been told that the central cavity of
the hydra (60) seems to fulfil the double purpose of a
heart and a stomach; but in the medusa this is much
more obvious.

124. In all the simple animals of which we have been
speaking, the functions of digestion (58) and assimilation
(47) appear to require no complex apparatus ; for their
food is taken into the stomach without previous prepara-
tion, and with very little, if any, selection, and the ordi-
nary contractility of cellular tissue is sufficient to effect
all the slow and gentle motions which are required for
their slender purposes. But, on the contrary, in those crea-
tures which are designed by Providence for a more exten-
sive range of usefulness, the purposes of life being more
numerous and important, the organization is proportion-
ably more various and complicated. The food, in sucli
beings, requires preparation before it is admitted into the
stomach. If it be solid, as is most frequently the case, it
must be broken down by some suitable machinery before
it can be swallowed. This process requires the presence
of certain firm and hard organs to crush the food. Hence;
the solid jaws and teeth which we observe in all the
larger animals and man ; — in whom the process by which
the food is crushed and prepared for being swallowed
is termed mastication, and the set of organs by which it
is effected is called the masticatory apparatus.

125. Even the solid teeth, which are found to com-
pose part of the masticatory apparatus of nearly all the
larger animals, appear much earlier than you would sup-
pose among the lower orders of creation. They are

ALIMENTARY CANAL. 73

found around the mouth of the sea-egg, a little animal,
the crust or shell of m hich you may see in almost any
museum, public or private. The jaws of the common
caterpillar you may observe at any time during the
summer, while the little animal is engaged in gnawing
the edge of a leaf. Its jaws are horny like those of all
insects, and not bony or composed of lime.

126. The masticatory organs of animals are not al-
ways confined to the neighbourhood of the mouth ; for
in the lobster we find, in addition to very complex jaws,
a set of teeth within the stomach itself, which enables
this singular being to chew its food even after it has been
swallowed. Many of the sea shell-fish have a long and
solid tongue covered with rough ridges and spines that
give them some powers of mastication. Not a few
of them have horny organs in the interior which are
much more powerful. There is a singular set of organs
of this character near the stomach of a little shell-
fish, lately brought from the coast of California by Mr.
Nuttal, the celebrated naturalist. In general form this
shell looks, to common eyes, very much like some of
our common fresh-water snails, and like them it lives
upon the edge of the water, breathing the air. It feeds
upon coral, which it swallows in fragments with the
animal adhering to it. The masticatory organs are
found at a considerable distance from the mouth and
near the principal stomach of this little animal. They
resemble three rasps bound together by circular fibres,
and occupy the whole of the passage for the food, so
that nothing can reach the stomach without passing be-
tween them. Now, the small portions of coral swallowed
by this shell-fish are so ground and broken by these files
that not only is the animal matter or food torn off from
them, but the very stems of hard lime on which the
polypi of coral grow, are formed into little rounded
pebbles which fill the intestines below the stomach.

127. The passage through which the food is conveyed,
in all animals that have such a passage, (for you see
that the Portuguese man-of-war has not,) is called the
alimentary canal.

74 ALIMENTARY CANAL.

128. The organs which masticate food after it has
passed fairly into the alimentary canal, are generally
called gizzards, and this name has been given to the appa-
ratus just described ; something similar to which is found
in many shell-fish,

129. Gizzards, or internal masticatory organs, are
found chiefly in those animals which have no jaws ; as in
the shell-fish; and in those whose jaws are too weak to
crush their proper food ; such as birds which live upon
hard grains, after the manner of the common fowl, the
turkey, &c. In birds, the gizzard is not provided with
anything resembling teeth, being composed of a very firm
flesh, lined with a hard, horny matter, and posessing so
great a degree of contractile power that the gizzard of a
turkey has been known to break to pieces a steel needle
without being at all injured thereby. The domestic
fowls are in the habit of swallowing hard pebbles, and
these supply the place of teeth in assisting them to grind
their food. When deprived of pebbles, they never con-
tinue healthy, and are apt to die of indigestion.

130. You can very readily understand that the more
nearly the food of an animal approaches in its nature
to the substance of the animal that subsists upon it, the
easier it is for the digestive apparatus to act upon it ; and
you will naturally infer that when the process of assimi-
lation is simple, the alimentary canal will be proportion-
ably simple. vSuch is the fact. In those animals that
live upon meats, or are carnivorous, the alimentary canal
is usually short and straight ; its most essential portion,
the stomach, is not complicated, and digestion is rapid.
But, on the contrary, in those animals that feed on vege-
tables,— which, though composed of organized matter,
differ very widely in their organization from the animal
frame, — the labour of digestion is much greater, and the
digestive apparatus more involved.

ALIMENTARY CAXAL.

Alimentary canal of a
limpit.

131. To obtain some idea of the
very complex character of the diges-
tive apparatus observed even in ani-
mals which you may consider insig-
nificant, you have only to examine
fig. 23, which represents the alimen-
tary canal of the common limpit, a
little shell-fish adhering to rocks on the
sea-coast. M represents the mouth of
this animal ; T is the tongue ; S the
stomach, and O the intestine wound
round and folded upon itself so as to
occupy but little space.

132. Now, in many fishes and birds
of prey, the alimentary canal passes
almost directly through the body, and
the stomach is but a slight enlargement of the canal,
while many other animals not only have much more
complicated intestines, but are provided with other en-
largements of the canal besides the stomach, such as the
craw or crop in pigeons and fowls. All beasts that
chew the cud, or ruminate, such as the ox and the sheep,
have four stomachs in the place of one, and each of
them has its own peculiar duty to perform in effecting
the digestion of the food. The first of them, for instance,
receives the food when it is taken, and retains it for
some time, until the animal is at leisure to chew it more
deliberately. It is then passed into the second stomach
to be there moulded and thrown up in small parcels into
the mouth again to be fully masticated; after which it
descends into the following stomachs, which continue
the process of assimilation. Connected with the alimen-
tary canal of the camel we find receptacles for contain-
ing pure water, which enable this animal to traverse the
wide and arid deserts of Africa, where water cannot be
had. The traveller in these deserts is often preserved
from death, by thirst, in consequence of the supply of
water obtained by killing one of his camels.

CHAPTER V.

ON THE NECESSITY FOR A SPECIAL APPARATUS OF MOTION — •
THE MUSCULAR AND OSSEOUS SYSTEMS AND THEIR APPEN-
DAGES.

133. By this time you must perceive, very plainly,
that the motions, both internal and external, performed
by animals of much more elevated rank than the polypi,
are far more numerous and powerful than theirs. The
force required to break down the solid food on which
many of them subsist, by means of firm organs, such as
teeth, jaws, or gizzards, is much greater than the soft
and delicate cellular tissue of an animal could exert.
Such beings, therefore, require, and are consequently
provided with, a separate system of contractile organs,
called the muscular system. The muscles which compose
this system display prodigious powers of contractility
and, when called into action, they draw together the
parts to which they are attached with a strength that is
altogether astonishing, when w^e consider their softness
and apparent tenderness. Thus a strong man can rise
upon his toes while lifting a weight that requires the
muscles of the calf of the leg to exert the force of a
ton and a half. Yet so completely is this strength de-
pendent upon the principle of life, that, immediately after
death, a small portion of the force just mentioned is
sufficient to tear the organs to tatters.

134. The muscular system, then, is the apparatus by
means of which the more perfect animals perform all
motions that are very prompt, and all those that require
much force. The limbs and body are provided with
muscles to enable them to perform all their mechanical
actions; the alimentary canal is also surrrounded with
muscles to propel the food from place to place, as the

VOLUNTARY AND INVOLUNTARY MUSCLES. 77

progress of digestion requires such changes, &c. But,
these motions, being extensive and performed only when
occasion requires them, seem to be dependent on a to-
tally difterent kind of stimulation from the tonicity that
the muscles display at all times, in common with most
other parts of the body, (114, 115). You should, there-
fore, avoid confusing the more active muscular contrac-
tion, which appears to be the result of the action of pe-
culiar stimuli upon these organs, with the tone of the
muscles, which is the result of causes producing the
same constant contraction of all other parts.

135. As some of the motions of a complex animal,
such as those which are designed to carry him about in
search of food, or to masticate that food when found,
require to be under the government of the will, the mus-
cles which perform these motions are called the muscles
of voluntary motion.

136. But the motion of the food during digestion and
those other operations upon which the growth and nu-
trition of the body depend, could not be trusted with
safety to the control of the will, lest the passions, the
follies, or the indiscretions of the animal should be con-
tinually arresting or embarrassing those operations, thus
destroying all security for the continued health, and per-
haps the life of the individual. Providence has there-
fore wisely ordered that the muscles upon which these
motions depend shall act under the impression of their
proper stimulants, without the control or the conscious-
ness of the animal. They are, therefore, called the in-
voluntary muscles.

137. The acts which are performed by the involun-
tary muscles are such as are necessary to the functions
of assimilation and nutrition, the digestion of food, the
absorption and circulation of the nutritive fluids, the
growth and the support of the organs. Now these vital
functions are common to all organized beings ; they are
functions of organic life (101); and hence the muscles
of which we are now speaking are called the muscles of
organic Z^e— while the voluntary muscles, which do not

78 APPARATUS OF MOTION.

directly contribute to the same processes, but to others
which are peculiar to animals, are called also the muscles
of animal life.

138. There are certain operations directly connected
with organic life that cannot be safely entrusted to the
absolute government of the will, on the one hand, nor
entirely removed from its control on the other. Thus
life cannot be supported for more than a few minutes
without breathing, but it would be impossible to carry
on the ordinary business of life if man were compelled
to breathe at all times, or at perfectly regular intervals.
Again : If obliged to attempt an inspiration v,^hen under
water, or when the head is immersed in a poisonous air
or gas, the consequence would be fatal. The muscles
that perform the motions required in breathing are, there-
fore, partly under the control of the will, but after they
have been at rest for a short time, no determination on
the part of the animal can prevent them from recom-
mencing their functions. Muscles of this character have
been termed, rather rudely, the mixed muscles.

139. It is now time to give you a clearer idea of the
nature of these highly important organs. You have
been told that when you have removed the skin of a
quadruped you find beneath it a layer of simple cellular
tissue, perhaps containing a portion of fat (71). If you
remove this by dissecting it off, you will find, in most
parts of the body, a broad smooth expansion of a pearly
hue, covering a red substance beneath. It is sometimes
thinner than the finest paper, and almost perfectly trans-
parent; in oth;T places it is thick, white, and nearly
opaque; while in many situations it is altogether want-
ing. This membrane is composed of condensed cellu-
lar tissue, strengthened by numerous fibres which are
generally disposed very irregularly over and through its
substance. It is called a fascia.

140. In reading works on physiology or medicine,
you would find mention made of many fascias in differ-
ent parts of the bod)^ ; but in ideality these are all con-
nected together in various ways throughout the whole

FASCIA MUSCLE.

frame, so as to constitute something like a distinct
system.

141. The principal uses of fasciae are to separate
parts from each other by interposing between them
something more resisting than the loose and soft com-
mon cellular tissue, and to bind down various muscles
or sets of muscles, so as to give them proper and grace-
ful form, and prevent them from starting out of their
position when they contract. They also arrest or retard
the passage of the fluids from cell to cell through the
cellular tissue in some forms of dropsy, and exert a
powerful influence in limiting the progress of inflamma-
tion or other local diseases, which pass through the
fasciae with great difficulty.

142. These fasciae are found, not only near the surface
of the body, beneath the skin, but are met with between
the deeper seated organs, which they surround, cover,
or envelope more or less completely, in many places.
Were it possible to remove from the body all its harder
portions, all its special organs, and all the loose or com-
mon cellular tissue, there would remain nothing but a
series of large cells or cavities, of various sizes and
shapes, composed of the fasciae. Many of these cells
would be found imperfect, communicating freely with
each other in consequence of the deficiency of their
walls. If you now recall to mind the fact that these
fasciae are really composed of common cellular tissue
strengthened by fibres (139), and that they are embedded
in, and continuous with that tissue on all sides, you will
have an idea of these 'parts sufficiently clear for our
present purpose.

143. When you cut through the superficial fascia, in
a quadruped (139), you find, in most parts of the body,
the bulky red substance which we call jiesh. To a
casual observer, this flesh appears like a rude mass of
matter designed to give form to the body, and to supply
food for man and other animals. Such is indeed the
popular idea of its nature, but the physiologist informs
you that it is composed of a great number of distinct
organs designed for the production of active and exten-

APPARATUS OF MOTION.

sive motions. Each of these organs is a muscle, and
the whole mass of flesh taken together constitutes the
muscular system.

144. Each muscle (except the hollow involuntary-
muscles, of which I shall speak hereafter) is attached
at either end, to the parts which it is intended to draw
together, but is generally disconnected from all other
organs every where between its extremities. It is found
enveloped in a delicate sheath of cellular membrane,
and is surrounded by loose cellular tissue, sufficient to
allow it to move freely ; but the layer of this substance
in which it is embedded, is often so thin that the eye
cannot very readily distinguish the separation of the side
of one muscle from that of its neighbour; and this is
the reason why the flesh of a hmb is taken for an undi-
vided mass by the ignorant. The skilful anatomist, how-
ever, readily dissects around the entire circumference of
a muscle by cutting through the loose cellular tissue only,
without wounding the flesh in the least.

145. In fig. 24, you see part of a muscle thus dis-
sected, to show its form when every thing, including the

Fig. 24.

Biceps muscle.
>, Fleshy portions of the muscle, c, the tendon.

STRUCTURE OF MUSCLE.

bones to which in this case its extremities are attached,
has been removed from around it. This is part of the
double muscle of the arm, whose function it is to bend
the fore-arm.

146. When we examine a muscle more closely, we
find it apparently composed of a great multitude of fibres,
each surrounded by its own envelope of cellular tissue.
These fibres are generally collected together in small
bundles, which are again associated into larger groups
forming the whole substance of the organ. Each bundle,
and, indeed, each particular fibre, enjoys its own parti-
cular power of contraction ; so that some parts of a large
muscle maybe called into action while other parts remain
at rest ; and thus the same organ may produce various
motions, according to the direction of the fibres that
happen to contract. Irregular motions of one or more
fibres often occur from diseases, such as convulsions or
cramp.

147. The muscles of man and the more complex
animals are of a bright or deep red colour : but those of
animals whose blood is white, such as the insects and
many other minute beings, are pearly, colourless, or
sometimes even transparent.

148. The attempt has been often made to determine
the actual structure of the muscular fibre by means of
powerful microscopes, and some writers tell us that it
consists of a row of red globular bodies connected
together by transparent matter. Others inform us that
no globules really exist in it, but that it resembles a cord
or riband, crimpled on the surface, as if thrown into
zig-zag folds by its own contraction. One celebrated
physiologist of the present day declares that each seem-
ing fibre is nothing else than a very long and narrow
cell, containing a fluid. Now the fact is, that such
examinations, made wdth very pow^erful lenses, require
a degree of knowledge, practice, and judgment which
few men in the world possess ; and so numerous are the
sources of error, that very httle dependence can be
placed on the results. This investigation is highly

82 APPARATUS OF MOTION.

important to the profound physiologist, but it would
only tend to confuse the mind of the elementary student.

149. Whatever the true structure of the muscular
fibre may be, it is well known that the common cellular
tissue, which seems to form the entire body of the
simpler animals, penetrates the muscle in every part, so
that when every thing peculiar to the organ has been
removed by art or disease, there still remains a mass of
that tissue occupying the same place.

150. Sometimes, when bones are broken, a piece of
muscle is caught between the broken extremities : the
fragments cannot then be knit or reunited until the vital
powers have caused the absorption of all the muscular
matter that intervenes ; and it is found that the part is
then reduced to simple cellular tissue, which does not
interfere with the knitting ; for, new bone is soon de-
posited in the tissue, and speedily joins the fragments
together.

151. You can readily understand that the muscles
would perform their office very awkwardly, (at least in
the more complex animals,) unless attached at their
extremities to parts more firm than mere cellular tissue;
for how could the body be moved to any useful pur-
pose, if there were nothing about it to prevent it from
bending with equal facility in every direction ? Now
the necessity for such firmer parts is answered in widely
different ways in different portions of the animal king-
dom. You have been told that even the hydra has an
external surface composed of a cellular tissue more
dense, and consequently somewhat harder than the
other portion of its body (65) : and when we examine
animals of somewhat more complex structure, we find
that nature employs the true skin, — which is mainly
composed of the same tissue, very much condensed and
strengthened with innumerable harder fibres — as an
attachment for the voluntary muscles. She also em-
ploys, for the same purpose, the fascia? (139) or internal
membranes, which are rendered strong by means of the
fibres contained in their structure. The common snail

MUSCULAR ATTACHMKWTS.

found in the damp vaults in which we often keep our
meat and butter, will furnish you with an excellent idea
of an animal that performs many and curious motions,
and is provided with a multitude of muscles, the greater
part of which are connected with the skin. The pro-
gression in all such animals is very slow, and is effected
with seeming difficulty, because the parts to which the
muscles are attached are so soft and flexible that they
cannot be made to perform sudden and violent motions.

152. Many animals analogous in some respects to the
snail, and classed by naturalists under the general name
of mollusca or soft animals, have the power of secreting,
upon the external surface of their mantle — a membrane
formed by an expansion of their skin, that covers their
bodies loosely, like a cloak — a solid shell, composed
chiefly of carbonate of lime ; from whence this portion
of the mollusca are often called testacea. This shell
answers the purpose of a house to live in ; and although
the animal can never leave it, it can thrust the body out
or draw it back at pleasure, by means of certain large
and strong muscles attached to the shell w^ithin its cavity.
But even in such animals, all the muscles which enable
them to crawl and carry their shell about are connected
with the skin, which, in many places, is very thick and
hard. You can often find small snail-shells beneath
damp boards in the garden, in the moist earth about the
lower part of fences, or under the bark of decaying
logs or stumps in the woods. By the side of almost any
large brook or river you may gather quantities of shells
inhabited by animals of the same class, and if you keep
a few of these for some hours in a tumbler of water,
choosing such as have no hard covering over the mouth
of the shell when the animal retires within it, you may
now and then enjoy the opportunity of seeing them swim
upon the surface, displaying in the most beautiful man-
ner the slow motions produced by muscles which arise
from one portion of the skin and* are inserted into an-
other.

153. There is a large class of marine animals known
by the very hard name of echinodermata or sjpiny

84 APPARATUS OF MOTION.

skinned animals^ in which we find the true skin not
covered by a simple cuticle alone (96,) but also by a solid
incrustation of lime, enveloping nearly the whole body.
Some of these animals are formed like a star ; and in
these, ll e rays, which are often divided into many
branched'', are employed as limbs to walk with. The
hard incrustations of these rays and their branches are
divided transversely into very numerous segments or
rings bound together by a more flexible horny matter ;
and the muscles of locomotion, passing from one ring or
segment to another, serve so to bend them as to enable
the animal to move alonsj the sand at the bottom of the
ocean. You may find animals of this character dried,
and preserved in cabinets by the improper name of star-
fish. They are very common on the shores of inlets
from the sea.

154. In some of the members of this class, known by
the popular name of sea-eggs, there are no rays, the body
being of a form approaching to the globular ; but the
external surface of the incrustation is studded with raised
balls of the same substance, perfectly smooth and pol-
ished. To each of these balls a strong spine of solid
carbonate of lime, sometimes very thick and long, is
attached by means of a regular socket exactly fitting the
round surface of the ball ; and these spines are moved
by muscles attached to them, so as to enable the animal
to push or roll itself along. The sea-eggs are common
on sandy coasts in hot countries, and among rocks in
northern climates. You will find their shells or crusts,
(sometimes with spines attached, but more frequently
without them) in almost every collection of shells.

155. I need not explain to you the manner in which
insects and also crabs {crustacea) employ the jointed
horny or calcareous plates which are formed in their
cuticle and bound together by it. To make yourselves
acquainted with the motions of insects, you have only to
examine a fly or beetle ; and if you live so far from the
sea that you cannot procure a common crab or a lob-
ster, you can find a crawfish at any time by turning
over a few flat stones in the nearest rivulet where the

THE OSSEOUS SYSTEM. 85

water runs rapidly. The muscles of locomotion pass
from one segment to another in these animals, as they
do in the star-fish.

156. The external hard coverings, or, as they may
be termed, the external skeletons, of the testacea, the
echinodermata, insects, and Crustacea, may all be re-
garded as appendages of the skin, being secreted by
that membrane, as the solid stems of coral are secreted
by the bodies of the polypi (95, 96.) They resemble
more or less the nails, horns, scales, and beaks, of man,
quadrupeds, fishes, and birds. Like the outer bark of
plants, these parts possess no life, and are subject to
being worn away by friction and injuries, and afterwards
reproduced. Insects and Crustacea cast off their hard
covering at certain seasons, and form new ones adapted
to their changes of shape and dimensions.

157. But you will readily conceive that external
skeletons like those of the Crustacea and insects would
be very ill adapted to the necessities of the larger and
more important animals. The accuracy of the sense
of feeling would be destroyed over nearly the whole
body by such an arrangement, while the freedom of
motions would be greatly impeded by the rigidity of
the envelope. The bulk, weight, and rapid and power-
ful motions characterizing the members of the higher
orders of the animate creation seem also to require a
solid internal frame-work, to give strength to their
several parts. Accordingly, we find the reptiles, fishes,
birds, quadrupeds, and man provided with another sys-
tem of solid organs, situated within the body, and con-
nected together by numerous joints. This is called the
osseous system, and the individual organs which compose
it are the bones.

158. All the voluntary, and most of the mixed muscles
are either directly or indirectly connected at each ex-
tremity with the bones ; and it is by the motions of the
osseous system, produced by these muscles, that all the
voluntary actions of the animal are effected. Nothing
analogous to true bone is found in animals of less dignity
than the reptiles and fishes.

86 APPARATUS OF MOTION.

159. Even the bones of the most perfect animals are
soft and flexible at a very early age ; and, at a somewhat
later period of existence, a portion of almost every bone
is still found in the same condition. It is not very un-
common to see the arm of a child two or three years
old bent and deformed by a fall, without being actually
broken ; and it may be then restored to its proper shape
by the surgeon without producing a fracture. Bones
are originally formed of soft cellular tissue, filled with a
kind of glutinous fluid. After a time, this fluid is gra-
dually absorbed, and a white, elastic substance, resem-
bling what anatomists call car^//«^e, commonly known by
the name o( gristle, is deposited in its place. The bones
then become firm enough to be useful to small or very
young animals, and also to some beings of much larger
size, that, living entirely in the water, have their weight
supported by the fluid in which they float, and are there-
fore less liable to falls and heavy blows. A very large
family of fishes are found to possess an entire skeleton
composed of gristle alone. Even the jaws of that terri-
ble animal the shark, are composed of this material, and
a portion of the ribs, in man, remains in the same con-
dition during life.

160. But the necessities of most of the more perfect
animals, when full grown, demand a skeleton or bony
frame-work for the body, that is very hard and inflexible.
The bones are brought to this condition by the deposition
of earthy matter within the substance of the gristle ; and
this deposition becomes at last so considerable that these
organs appear to be entirely composed of it. Two salts
of lime, the phosphate in great abundance, and the car-
bonate, or common chalk, in small proportion, constitute
nearly the whole of this earthy matter.

161. If we heat a perfect bone for a long time in a
furnace, all the gristle will be burned out, and the whole
will crumble easily under the fingers like a piece of
chalk, because the animal matter that bound the earthy
particles together has disappeared. By long boiling in
water, much of the animal matter may be removed, and
the bone reduced to nearly the same condition.

STRUCTURE OF BONE.

162. On the other hand, if we place one of these organs
in a large quantity of dilute acid, the earthy matter will

be gradually dissolved, as in the case of the eye-stone
surrounded by vinegar (13) ; and then the gristle will
remain, preserving the form of the bone most perfectly,
yet becoming so flexible that it may be tied in a knot
without breaking, if the specimen be long enough for the
purpose. One of the bones of the fore-arm reduced to
this condition and thus tied, may be seen in fig. 25.

163. By a careful and diffi-
cult process even the gristle
maybe removed, so as to leave
nothing but the soft cellular
tissue in and by which the
bone was originally formed.
By preparing a bone thus re-
duced with spirit of turpentine,
it may be rendered so tran-
sparent that you can read a
book through its thickness.

164. The changes thus ef-
fected by art, are often accom-
plished in the living body by
disease. There is a very ter-
rible affection sometimes seen
in Europe, but scarcely ever
in this country, which reduces
ail the human bones nearly to
the condition of gristle, so that
they will bend with the weight
of the body or the limbs, until the unfortunate patient
becomes' horribly deformed and finally dies. In scro-
fulous or cancerous complaints, a part or the whole of
a particular bone may be reduced nearly to simple cel-
lular tissue; — and in consequence of this change, I have
known a person to break an arm by simply turning in
bed. In a few rare instances, the gristle and earthy
matter have been restored by the vital powers after such
an alteration.

165. From v/hat has been already said of the struc-

Bone deprived of earthy matter.

88 APPARATUS OF MOTION.

ture of muscles and bones, you are now prepared for
the statement of a general truth, which I introduce in
this place in order to avoid the necessity of frequent
repetition. Every part of the body of an animal, and
consequently every organ that it contains, is composed,
in part, of cellular tissue : after death, it may be reduced
by art to the condition of simple cellular membrane.
Any organ not essential to life may undergo this change
in consequence of disease, and may be restored by the
vital powers to its former condition.

166. This membrane, which, as you have been told,
seems to form the entire body of the simplest animals,
such as the hydra (65), is really the instrument by which
all the organs are created. There is a time in the history
of every animal before birth, when the body is composed
entirely of cellular membrane, and is as simple in its
structure as the hydra. The younger an animal is, the
more nearly all its organs approach to this simple state.

167. When an earth-worm is cut in half (43, 44), it
is the cellular tissue that grows, so as to form a new
head or a new tail. And when the leg of a salamander
(a little water lizard) is bitten oft' by a bird, or a fish,
the same tissue buds out, like the branch of a tree, and
forms a new limb, gradually constructing within itself
the bones, the muscles, and all the other organs belonging
to the perfect member. So, in man, when he is wounded,
it matters not whether the injury occurs in a bone, in a
muscle, or any other particular organ, it is always the
cellular membrane that first unites or heals, and the
matter peculiar to the organ is afterwards deposited
within it.

168. Why it is that cellular tissue should form a bone
in one part of the body, a muscle in another, &c., we
know not, because the principle of life — the power that
regulates the vital functions — is a mystery beyond the
reach of human learning.

169. But let us return from this digression. It is
scarcely necessary to tell you that the skeleton is com-
posed of a great man_y bones, most of which are con-
nected together by movable joints. If the extremities

CARTILA.GE SYNOVIAL MEMBRANE. b9

of the bones at the joints were pernfiitted to come in
contact with each other, without the interposition of any
softer matter, there would be great danger that the
edges of the bones would be broken off in consequence
of slight falls, blows, or violent motions ; for bone is very
brittle, and cannot be compressed. To guard against
this danger, the extremities of the bones, where they
form movable joints, are covered with a thick cap of
white elastic matter called cartilage.

170. Cartilage bears a strong resemblance to the
gristle of which the entire skeletons of many full-grown,
and those of all very young animals are formed (159),
and hence anatomists have termed the elastic covering
of the joints the articular cartilages, to distinguish them
from all other organs of somewhat similar appearance.

171. You may examine for yourselves the structure
of the articular cartilages in the joints of any of the
larger animals when cooked for the table; for, although
the process of roasting or boiling alters them considera-
bly, they will still serve your purpose very well unless
they have been overdone. A knuckle of veal or a pig's
foot wnll furnish you with the best example, and may be
examined in the kitchen before it is dressed. One such
examination will give you clearer ideas than a volume
of description.

172. To prevent friction between the articular carti-
lages when the body is in motion, every movable joint
is provided with a delicate sac of very thin and perfectly
smooth membrane, called a synovial membrane. This
lies between the articular cartilages, covering them so
closely wherever it touches them that it can scarcely be
separated from them ; but at the sides of the joints the
membrane is much less closely connected with the sur-
rounding parts ; so that it may be more readily seen.
The synovial membrane or sac always contains a small
quantity of a peculiar unctuous fluid called synovia^
which answers the same purpose with the oil that we
pour upon the axle or pivot of a wheel to make it turn
more easily; and this fluid is secreted by the mem-
brane which contains it.

90 APPARATUS OF MOTION.

173. When we were speaking of that form of con-
tractiUty which is called toincity (115, 116), you were
informed that the habitual tone of the muscles keeps the
bones, or rather the articular cartilages, always pressed
against each other with a certain degree of force. But,
in extensive and sudden motions of the members, the
bones would be continually liable to be put out of joint,
or dislocated, were they not bound together by some
firmer material than muscle, and one less capable of
being stretched or contracted. To secure the animal
against such accidents, the joints are provided with an-
other set of orojans called ligaments.

174. The ligaments are composed of cellular tissue
very much condensed, and strengthened by strong and
numerous fibres. They are white like the fascioe, in-
elastic, and cannot be suddenly stretched to any consi-
derable extent except by most violent forces. Though
flexible like membranes, and soft to the touch, they are
much stronger in proportion to their size than the bones
which they bind together. Their principal function ap-
pears to be the prevention of too extensive motions in
the joints; for many of them remain perfectly loose
while the bones are in an easy or common attitude, but
when they are bent as far as they are intended to go,
some of the ligaments are drawn tight, like cords, and
thus prevent either the muscles or slight accidents from
moving the joints any further. Let me give you an
illustration. The leg, in man, is intended to bend back-
ward in walking, and to remain straight in standing. It
can be bent backward until the heel touches the thigh,
without straining any of the ligaments, because the thigh
itself prevents it from being carried further in this direc-
tion than is suitable to the wants of the animal. But if
you endeavour to bend the leg forward or to either side,
you soon find it impossible, because there are very
pow^erful ligaments on the sides and in the interior of
the knee joint, which are put on the stretch whenever
you attempt to cause such a molion. Tremendous
forces sometimes dislocate the strongest joints; but,
whenever this occurs, either some of the ligaments are

LIGAMENTS PERIOSTEUM.

Fig. 26.

brolven, or the parts of the bones to which they are
attached are torn off. The latter accident is even more
frequent than the former. In fig. 26 you have a repre-
sentation of the hgaments of the elbov;^ joint.

175. You have been told
that each of the muscles is
inclosed in a kind of sheath
or covering of cellular mem-
brane or fascia (144). Each
of the bones is inclosed in a
similar manner by a mem-
brane composed of cellular
tissue strengthened by very
numerous and irregular
fibres, so that its structure
bears considerable resem-'
blance to that of the liga-
ments. As we may have
occasion to mentionthis kind
of membrane again it is well
to name it at once. It is
called the periosteum.

176. The periosteum ad-
heres very firmly to the bone,
and covers all parts of it,
except those which give ori-
gin or insertion to the liga-
ments and muscles, and those
w^hich are coated with car-
tilage. In some places, the

r.prm<stpnm ic f^^rtt^rtdf^f] nvpr '^' The bone of the arm. J, c, Bones
periosteum is exienaea over of the forearm, d, a lateral ligament

the surface of a cartilasre ; f ^^^e eibow joint, e. The capsular

CD ' ligament of the elbow joint. /, A liga-
and the membrane then takes nient connecting the bones of the fore-

another hard name. It is^^'"'

not essentially changed in its nature, and it is hardly
right to task your memory with its title It is called
the perichondrium. The periosteum covering the outside
of the bones of the skull has received the name of peri-
cranium.

111. Having now enumerated the principal classes of

Ligaments of the Elbow Joint.

92 APPARATUS OF MOTION.

organs, &c., that belong or are appended to ihe osseous
or bony system^ namely ; the bones, the cartilages, the
ligaments and the periosteum ; let us return for a few
moments to the muscles.

178. Most of the voluntary muscles are large, for
they are designed to exert great force. Now, if they
were so formed as to preserve the same fleshy and
bulky character throughout their whole extent, the
joints which they surround or cover in their passage
from one bone to another would be buried as deeply as
any other parts of the bones. The elbow would be at
least as thick as the arm, and the knee would rival the
calf of the leg. Moreover, the bones would not present
suflicient surface for the attachment of such a multi-
tude of fleshy fibres. All symmetry of form would be
destroyed, and the strength would be exceedingly
diminished. But, to prevent these inconveniences, the
muscular fibres of many of the principal voluntary
muscles are made to terminate in much finer fibres of a
pearly hue, possessing far greater strength than those of
the red, fleshy portion of the muscle. These smaller
fibres are crowded together so as to occupy very little
space in comparison with the more bulky part of the
organ. Any bundle of such fibres which may be con-
nected with a single muscle is called a tendon. A
drawing of one of these accessories belonging to a
double muscle is seen at fig. 24, where a and b repre-
sent portions of the two fleshy bellies of this muscle,
both terminating in the single tendon c.

179. Some of the tendons are round, like a cord, and
others are flattened until they resemble a very thick
fascia, from which, indeed, they do not difler very
widely in composition. One of the former kind you
may examine in your own person by grasping the back
of your ankle an inch above the heel. The thick hard
cord that you feel there is a tendon connected with the
muscles that make the foot point downwards, or lift the
whole body when we stand on the toes. Small as it is,
every fibre of the flesh composing the bulk of the calf
terminates in it.

ARRANGEMENT OF TENDONS. 93

180. The tendons do not contract like the fleshy-
fibres, nor can they be stretched any more than the
ligaments (174). They act like simple ropes or bands
to connect the ends of certain muscles with the parts
that those muscles are intended to move. The me-
chanical arrangements of the tendons in the larger
animals and man are often exceedingly curious. Some
of them run over pulleys formed by grooves in the bones
near the joints, which pulleys are covered with cartilage
and synovial sacs to prevent friction (172). Sometimes

Fig. 27.

Section of the Orbit. The Human Eye and its Muscles.
a. The outer straight muscle of the eye, cut off from its attachment at the bottom
of the orbit, and turned up to display the other parts. 6. c, </, The other straight
muscles, e, The superior oblique muscle, with its tendon running through a car-
tilaginous pulley near the edge of the orbit, and turning back to be inserted on
the outside of tlie globe of the eye. /, The optic nerve.

they are bound down in their places by ligaments which
stretch across the grooves. Some of the tendons are
perforated by smooth openings, resembling button-holes,
through which other tendons pass to reach their destina-
tion. But one of the most curious of these arrangements

91 APPARATUS OF MOTION".

is seen in an oblique muscle of the eye, of which the
tendon runs through a pulley within the orbit, and then
doubles itself backward, so as to move the eye in a direc-
tion opposite to that of the motion of the muscle. (See
fig. 27.) If you wish to examine the action of a tendon
for yourself, take the leg of a dead bird ; cut off the
skin with a sharp knife, and draw with your fingers
any of the white cords that surround the bone. You
will immediately see a motion produced in the foot or
claws, and the kind of motion will depend upon the
tendon which you happen to have seized. In birds,
some of the tendons are often partly composed of bone ;
and the cap of the knee in man, though a bone, appears
to belong rather to the great tendon of the muscles on
the front of the thigh than to the skeleton, with which
it is not directly connected.

181. The involuntary muscles are rarely provided
;"with tendons. They are scarcely ever formed into dis-
tinct masses, like the voluntary muscles ; but, are nearly
always composed of fibres interlacing or overlapping
each other in various directions ; and, instead of being
connected with the bones or hard parts of the animal,
they are usually found spread out, like a membrane,
around some hollow organ, such as the stomach for
instance, to which they furnish a distinct coat called
the muscular coat. When called into action, the fibres
of the muscular coat contract in such a manner as to
expel the contents of the organ that they envelope. All
parts of the alimentary canal of the more complex
animals are provided with a muscular coat, designed to
drive forward the food and its products, as the process
of digestion advances.

CHAPTER VI.

ON THE GENERAL DIVISIONS OF THE VASCULAR SYSTEM.

182. Many of the organs that have been mentioned
are large and solid. Their structure, and, consequently,
the materials of which they are composed, are very
various. In some of them we observe many different
kinds of matter combined to form a single organ. Thus :
in each of the bones, when perfect, there are found the
cellular tissue, the cartilaginous matter, and the earthy
substance or lime (160). Now these various and often
very complex organs, must be provided with the mate-
rials necessary for their growth and support from the
same nutritive fluid; and you will naturally conclude
that it would be scarcely possible to convey this fluid
throughout all parts of a machine so complicated, by
suffering it to pass from cell to cell through the whole
body, as in the polypi (59, 60.) Nor could it be more
conveniently distributed by means of a stomach branch-
ing and sending canals to every part, as occurs in the
medusa (122). Accordingly, we find that in all the more
important animals, the nutritive fluid formed by the
process of digestion in the alimentary canal, instead of
being absorbed into the general cellular tissue, as in the
hydra, &c. finds its way, by a process that will be ex-
plained hereafter, into a great number of minute ves-
sels, canals, or tubes, that all tend toward some common
centre or receptacle in the substance of the body, en-
tirely distinct and removed from the alimentary canal.
These tubes or canals are known by the general name
of the blood-vessels, and the nutritive fluid having been
sufficiently prepared to enter them by the first steps in the
process of assimilation (47, 48), is then properly called
the blood.

VASCULAR SYSTEM VEINS.

183. The blood-ves-
sels through which the
blood flows toward the
common centre just
mentioned, are called
the veins; and in ani-
mals placed high in the
order of nature, the mi-
nute veins are found in
every part of the body
in countless numbers.
To obtain some idea of
their number and ar-
rangement, you may
glance at the figure of
the venous system in
man, as represented in
fig. 28.

184. The blood in the
veins is constantly flow-
ing toward the common
centre or receptacle
(182) ; for these vessels
are generally provided,
internally, with nume-
rous valves or flood-
gates, which will not
allow any thing to pass
in the opposite direction.
The structure of these
valves you will be better

prepared to understand The General Venous System.

hereafter, but fig. 29 will convey some idea of their ap-
pearance in a vein that has been laid open.

185. The common centre or receptacle is very dif-
ferently constructed in different animals. In insects and
worms it is merely a single very large blood-vessel,
running lengthwise along the bacl\, and provided with a
muscular coat or some such contrivance to force the
blood forward towards the orizans ihat it is intended to

VALVES OF THE VEINS.

nourish. In the higher
orders of animals, it is
a very strong hollow
nnuscle, designed to re-
ceive a small quantity
of blood at a time, and
then, by contracting, to
urge that quantity on-
ward. The receptacle,
when constructed in
this manner, is called
a heart ; and the beat-
ing of the heart, as it
is called, is produced
by the motion of this
most important organ
in pumping its con-
tents.

186. When the blood
from the veins has filled
the heart or the great
vessel that answers the

same purpose, it is ne-
cessary that it should
be conducted through

A Vein laid open to show the Valves.

a. The trunk of the vein ; h, b, the valves;
c, a branch of the vein entering it.

another set of channels to all parts of the body, and into
the substance of every organ, in order to nourish it. For
this purpose another set of blood-vessels, called the arte-
ries, is provided. One or more great arteries originate
from the heart, and pursue their course toward the ex-
tremities. Each artery soon branches into two or more
trunks, and each trunk is again and again divided, until at
length the number of branches exce-eds all calculation ;
and there are few parts of the body into which a pin can
penetrate without wounding one. For a general idea of
the distribution of the arteries in man, you may refer to
the view of the arterial system as represented in fig. 30.
187. The current of blood produced by the action of
the heart is very rapid; and you are not to suppose that
any part of the body employs all the blood which is sent

THE VASCULAR SYSTEM.

to it for its growth or
sustenance. In fact a
very small proportion
of the whole amount
is actually converted
into cellular tissue,
muscle, or other solid
nnatter, in the course
of a single day. But
the heart drives for-
ward so much, at
every beat or pulsa-
tion, that, in a full
grown, heahhy man,
all the blood in the
body must pass
through that organ
sev^eral times in an
hour. You perceive,
therefore, the necessi-
ty of some connexion
between the arteries
and the veins, in order
that the blood driven
by the heart through
the arteries into the
organs, may be re-
turned through the
veins to the heart.
This communication
is effected by the con-
tinuation of the ex-
tremelv minute bran-

Tlie Getieral Arterial System.

ches of the arterial system into the equally minute roots
of the venous system: so that if you inject a large quan-
tity of coloured water into the principal artery of an
animal, soon after death, the water will pass into the
veins, and return through them to the heart. The small-
est divisions or ramifications of both sets of blood-vessels
are scarcely, if at all, visible to the naked eye; and as

SIMPLE FORMS OF CIRCULATIOrf. 99

they are as fine or finer than a hair, they are called by
physiologists the capillaries or capillary blood-vessels,

188. What you have now been told will give you
some idea of the nature of the circulation^ which is that
process by which the blood, in those animals that are
provided with blood-vessels, is kept continually in motion
toward and from every part of the body.

189. The more closely you study physiology and na-
tural history, the more you will be surprised at the gra-
dual and beautiful manner in which one organ is added
after another, as you proceed from the observation of
the more simple to that of the more complex animals ;
you will observe that each of the principal vital func-
tions, which, in the hydra, is performed seemingly by the
skin or the common cellular tissue, requires, in the higher
classes of animals, a peculiar system of organs ; you
will see this system rendered more and more complex
as animals rise in what has been termed the scale of
nature ; and the performance of the function will be
found more and more perfect in proportion to this com-
plexity. Common cellular tissue may digest well enough
to support the frame of a hydra (72,) but it is not sufli-
ciently active to nourish an insect : and insects have,
therefore, a very complex alimentary canal for digestion.
Again : The contractility of the cellular tissue alone may
be sufficient to drive the nutritious fluid to all parts of
the body of a polypus, but it would fail to answer the
same purpose even in an earth-worm; and an earth-worm
is, therefore, provided with blood-vessels and a proper
circulation.

190. In most perfect insects, (that is, in most of those
that have reached their full development, like the cat-
terpillar that has become a butterfly,) the circulation does
not appear to be complete. They have a large blood-
vessel running along their back, often terminating at either
end in some branches which have been supposed to open
into the general cellular tissue of the animal. In this
blood-vessel, which is highly contractile, the fluid is driven
onward in waves, sometimes in one direction and some-
times in the other, but generally from behind forwards.

100 THE VASCULAR SYSTEM.

This blood-vessel may be regarded as an artery ; but as
veins have been detected in very few insects, it is still
believed by many that the blood is merely agitated or
mixed in this vessel, which is supposed to receive it by
suction or absorption from the cellular tissue at one of
its extremities and at certain other places, and to drive
it out into the same tissue at the other extremity. In
several of the imperfectly developed insects, such as
those larvae* which come from the water and afterwards
form the dragon-fly, we find a complete circulation, and
these animals furnish us with the simplest example of a
circulatory apparatus. It consists of the dorsal vessel
just described, and another which may be considered as
a vein, running along near the under surface of the body.
These two vessels communicate with each other at either
end by means of numerous branches ; they both send out
several lateral ramifications to various parts of the body
and limbs, and there can be no doubt that these branches
communicate with each other in the substance of the
various organs. The blood in these larvae is seen to
flow from the tail toward the head, through the princi-
pal artery or dorsal vessel ; and, as it passes, it sends its
divided current into the smaller arteries till these become
too minute for examination. We can then detect it flow-
ing through all the little veins toward the principal vein
or inferior vessel, through which it is constantly moving
from the head toward the tail; whence it is forced to
return again into the dorsal vessel.

191. In the leech, and most marine worms, we find
several other large vessels running longitudinally, and
receiving a portion of the blood, for purposes that you
are not yet prepared to understand ; but, like the inferior
vessel, they return this blood to the great artery. Even
in animals apparently so insignificant as the oyster and
other shell-fish, but which take hiorher rank than the

*Most insects pass through at least four forms or conditions during
their lifetime. — 1. The egg. 2. The larva. 3. The pupa. 4. The
imago. In the silkworm, you may easily make yourselves acquainted
with these changes. The larva is the worm, the pupa is found wrapped
up in the cocoon, and the imago is the perfect fly.

CHYME AND CHVLE. 101

insects from their organization, we find the circulation
much more complex, for they have no longer a single
dorsal artery but a regular heart, sending the blood into
many sets of vessels. You will not be surprised, then,
to hear that the circulatory system in man is explained
with difficulty to those who have never considered that
system in those animals which are very simple in their
structure. After these remarks, however, I trust you
will find it an easier study when we reach the subject.

192. You have been promised an explanation of the
process by which the nutritive fluid makes its way from
the alimentary canal into the blood-vessels (182,) and it
is right to say a few words upon that subject here.
That peculiar kind of absorption seemingly resident in
cellular tissue, by which it takes into the body the nour-
ishment derived from the food in the hydra (59, 60) and
the medusa (122, 123,) is commonly called imbibition.
We know nothing of its nature, it is true, but we know
that it takes place, and it is therefore convenient to give
it a name, as we do when we call the power which
makes a stone fall to the ground attraction, though we
only know the simple fact that stones will fall to the
ground when unsupported.

193. By imbibition, then, it is probable that the nour-
ishment extracted from the food by digestion, (which
crude nourishment we call the chyme,) is taken into the
cellular tissue of insects, worms, and other animals with
a very simple circulation ; for we cannot trace any inter-
mediate passages between the circulatory and the diges-
tive apparatus in these animals. Now no openings are
known to exist in the sides of the blood-vessels; and
these vessels, like all the other organs of the body, how-
ever complex, are formed originally of the cellular tis-
sue. It is, therefore, reasonable to conclude that the
nutritive fluid, after entering the substance of the ani-
mals just mentioned, is carried thence into the blood-
vessels by imbibition.

194. But here I must pause to explain some other facts.
The chyme, while it remains in the alimentary canal,
is as yet imperfectly assimilated (47, 48,) and requires

102 THE VASCULAR SYSTEM.

further changes to fit it for entering the circulatory
apparatus. These changes probably commence at the
moment of its first imbibition ; and when it has once
entered the substance of the body, it is called the chyle.
Even the chyle is not exactly similar to the blood in
animals that have a circulatory apparatus, but requires
to be mingled with that fluid, and to circulate for a time
before it becomes fitied to nourish the several organs of
the body. These facts are ascertained by examinations
made upon the larger animals, and you will comprehend
them better hereafter.

195. In the higher orders of animals, the chyle is never
found wandering in the cellular tissue, as it may be, per-
haps, in insects, (190,) but is conveyed to the blood-vessels
through another set of vessels, called the lacteals. These,
though they supply the blood by carrying into it the
nourishment extracted from the food, are not a part of
the circulatory apparatus, but constitute a separate sys-
tem of canals passing from the bowels to the blood- ves-
sels— a system unknown in the simpler animals.

196. The chyle in the lacteals is always white or
milky, even in those creatures whose blood is red. Yet
it is an organized fluid, and contains globules, like the
blood and the sap of some plants (49), though of smaller
size than those observed in the arteries and veins.

197. The lacteals originate in countless numbers from
the internal surface of the alimentary canal below the
stomach. There is no reason to suppose that their
mouths stand open, so as to drink in the nourishment
from the chyme (19.3) as it passes ; but they imbibe this
nourishment through the cellular tissue, of w^hich their
sides are formed; so that there is no direct communi-
cation between the lacteals and the bowels. These
vessels, Hke the fine branches of the roots of a plant —
which seem to answer the same purpose in the vegeta-
ble kingdom — continually join with each other so as to
form larger trunks as they pursue their course toward
the centre of the circulatory system (182, 183,) until at
length they are all collected into one great canal, called
the thoracic duct, w^hich opens and pours its contents

THE LACTEAL VESSELS AND GLANDS.

103

Fig. 31.

into one of the largest veins of the body, just before it
enters the heart.

198. The lacteals are furnished
with valves, like the veins, to pre-
vent the chyle from flowing in any
other direction than towards the
blood-vessels ; but these valves are
much more numerous, occurring so
frequently as to give the vessels a
peculiar knotty appearance ; as you
see in fig. 31.

199. You have been already in-
formed (194) that the chyle is but
imperfectly assimilated w^hen it first
enters the body, and requires fur-
ther changes after it enters the
blood, in the route of circulation.
Now it appears that in those ani-
mals which are furnished with
lacteals the chyle is continually
changing, and becoming more and
more assimilated, from the moment
of its first imbibition until it reaches
the thoracic duct (197). In order
that time may be allowed for this
mysterious change, the lacteals pur-
sue a very winding course, and
every here and there they are
studded with little rounded bodies
— fig. 31, h, — into w^iich several
branches are seen to enter, and
from which a smaller number of
larger trunks usually make their
exit. These bodies are called
glands, and in their interior, the
little lacteal tubes are rolled and tangled together,
like a bundle of fishing-worms, so that they very con-
siderably increase the length of the route by which the
chyle has to travel toward the blood-vessels.

200. By this time you must be much less surprised

Lacteals.
Branches of the lacteal?.
b, A gland.

104 THE VASCULAR SYSTEM.

than formerly at learning that many of the simpler
animals may be cut to pieces without being killed. For,
if a polypus be divided, each piece is capable of digest-
ing its food, and may grow : — if a worm be cut in half,
each end has part of all its great blood-vessels and some
of their connecting branches left ; and it can still carry
on a circulation, provided the ends of the vessels con-
tract so as to keep it from bleeding to death: — but, in a
quadruped or bird, if the main trunk of the lacteals be
injured, the creature must starve, even though he may
continue to digest his food and his circulatory system
be in perfect order. His nourishment cannot then reach
the blood-vessels, and of course his organs cannot be
supported for any great length of time.

201. The lacteals, however, are not the only vessels
that convey substances into the circulation, though
there is every reason to believe that they furnish the
only very important route through which nourishment
can be introduced in the larger animals. Let me ex-
plain. If you put a blister upon any part of the body,
you can easily cut away the cuticle or scarf-skin (28),
so as to lay bare the true skin beneath ; but you do not
produce a wound, or lay open any blood-vessel by so
doing. Yet if you then dust the blistered surface with
certain medicinal powders, these will be found to act on
the patient precisely as if they had been taken into the
stomach : and, in most cases, these effects can be
rationally explained on no other supposition than that
part of the medicine is absorbed and carried into the
circulation. There is every reason to suppose that
water, mercury, and some other substances are even
imbibed through the cuticle so as to enter the blood.
When a poisonous snake has bitten any part of the
body, the poison very soon circulates and produces
the most serious consequences ; and I could recount a
thousand facts of a similar nature. Some substances
artificially introduced in the extremity of an animal,
through a wound, have been afterwards found in the
blood, and have been actually collected from it. Now,
here there are no lacteals to convey these matters into

THE LYMPHATIC VESSELS AND GLANDS. 105

the circulatory system. How, then, do they arrive at
their destination?

202. It is thought by many, that the veins of the part
may sometimes imbibe these substances directly. And,
indeed, we have reason to believe that, even in man,
the cellular tissue and the blood-vessels retain the power
of displaying all the functions that they perform in the
hydra, the medusa, or the earth-worm; imbibition among
the number (58, 59, 189) ; though these functions are
far too feebly exercised to supply the wants of so noble
a creature as the lord of creation.

203. But anatomy displays for us another route through
which these substances may and actually do reach the
circulation. We find in the more complex animals a
countless multitude of little vessels originating from
almost every part of the body, even from the interior of
almost every organ. These vessels are very much like
the lacteals ; but they are constantly filled with a colour-
less or slightly bluish fluid, called the lymph, and the
vessels themselves are called the lymphatics. The lymph
is always flowing towards the centre of the circulatory
system, and the vessels that convey it are continually
uniting into larger trunks, a great majority of which
empty into the general receptacle of the lacteals (197),
where their contents are mingled with the chyle before
it mixes with the blood. • The other lymphatics empty
directly into some of the larger veins.

204. To prove that the lymphatics do actually convey
to the circulation some of the substances mentioned at
paragraph 201, it is only necessary to state, that poison-
ed wounds not unfrequently produce most terrible effects
in consequence of the poison finding its way along the
lymphatics running from the part, which it inflames as
it goes, so that you can trace by the swelling, redness,
and pain, the extent to which the poison has travelled.

205. The lymphatics, like the lacteals, are provided
with glands, which are generally found larger and more
numerous about the principal joints than in other parts
of the body. The glands, in addition to the uses already
pointed out at paragraph 30, seem to act as guardians

106 FUNCTIONS TRIBUTARY TO NUTRITION.

against the introduclion of noxious substances into the
circulation ; for when a poison has reached one of these
organs, in following the route of a lymphatic or lacteal
vessel, the cellular membrane between the worm-like
folds of the canal (199), inflames and swells. The
glands being each inclosed, like many muscles and other
organs, in a firm covering of cellular tissue strengthened
by fibres not very easily stretched, this inflammation
frequently causes the vessel to close by the pressure of
the swelling, and cuts off' the route of the poison towards
the veins and heart.

206. The lymphatics are not discovered in the simpler
animals ; but, in those of the higher orders, they fulfil
most important purposes, which will be explained in the
next chapter. When spoken of collectively, they are
often called the absorbent system, and the individual ves-
sels are not unfrequently styled absorbents. These terms
are unfortunately employed by physiologists, for they are
calculated to deceive the student and to lead to the be-
lief that the lymphatics are the only organs capable of
carrying on absorption ; which is very far from the truth.
Should I use the term absorbent system in the after part
of this volume, you will understand me to allude to both
the lacteals and the lymphatics, and when the absorbents
are mentioned I do not wish to exclude even the veins,
for reasons given in paragraph ^02.

CHAPTER VII.

ON THE FUNCTIONS OF SECRETION, RESPIRATION, AND
NUTRITION.

207. You have received in the preceding chapter some
idea of the complexity of structure observed in the more
perfect animals. You have seen that this complexity
requires an extension and a corresponding complication

NECESSITY OF PERPETUAL SECRETION. 107

of the masticatory apparatus (124), and the digestive
system (130), in order to supply proper support to the
frame. The number of separate bones, muscles, and
other organs demanded to enable the animal to seek and
prepare food and to move it along the alimentary canal
as the process of digestion advances, requires that the
nourishing fluid in these animals should be confined in
blood-vessels (182), and conveyed to and from all parts
of the body by means of a circulatory apparatus (188),
which, in its simplest form, is composed entirely of blood-
vessels, but, in creatures a little more complicated, de-
mands a heart (185) as a principal moving power to
carry on the circulation. You have also learned that,
at first, the admission of the nourishment into the circu-
lation appears to be effected by simple imbibition (192,
193), but that as animals advance in the scale of nature
other assistance is required to convey it from the alimen-
tary canal into the blood-vessels. Hence the necessity
for the lacteals (195). You have been told, moreover,
that in the higher orders of animals certain substances
are carried into the blood from the surface of the body,
or from the interior of the various organs, and that for
this purpose the lymphatics are provided (202, 203).
Yet the circulatory system in all the more important
animals is much more complicated than you would sup-
pose, even from what you have learned heretofore ; and
in the present chapter I propose to introduce you to an
acquaintance with certain deeper mysteries connected
with it. In order to do this properly, I must quit for a
time the regular course of my narrative to communi-
cate some preliminary information.

208. It is easy to understand that, while an animal is
growing and forming its various organs, it must con-
stantly require food to supply the materials necessary
for its growth; and the circulation of the blood must be
continued regularly and perpetually. But why should
food be demanded, or why should the blood circulate,
after the animal has reached its full dimensions, when
its organization is complete and perfect? You may
reply that the wearing of the cuticle, nails, horns, or

108 FUNCTIONS TRIBUTARY TO NUTRITION.

Other externa] parts, demands a supply of food and blood
to make up for these losses; for such parts are contin-
ually growing as fast as they are worn away, even
at a late period in life. But a very small amount of
food and blood would be sufficient for this purpose ; and
yet the full-grown animal requires nearly as much food,
and has nearly as much blood in its vessels, as the young
one : why is this ?

209. If you place a vase of flow^ers, or a living plant,
under a bell-glass, you will find, in a few hours, that the
inside of the glass is obscured by moisture collected in
little drops all over the surface : and this experiment
proves that vegetables, which absorb water by their roots
(33, 34), actually give out water from their leaves and
branches. In like manner, the surface of animals
is continually pouring forth a fluid which we call the
persjpirotion. You do not see this fluid upon the surface
of organized beings at all times, because it is usually
thrown off' in the form of a gas that is invisible, and
combines immediately with the common air. It is only
when heat, exercise, or disease has increased very
greatly the flow of perspiration, that we see it collected
on the surface in the liquid form of sweat. But, to con-
vince you that the fluid is at all times escaping, during
health, you have only to bind closely upon your arm, or
any other part of the body, a piece of India-rubber cloth
or oiled silk, and, in a few hours, you will find the surface
beneath it completely wet, because the fluid discharged
from the skin cannot pass through the covering, and is
therefore compelled to collect in such quantities as to
arrest attention. If the experiment be long continued,
the sweat will generally ooze out round the edges of the
cloth and flow down the limb. The escape of gaseous
moisture from the skin is called insensible 'perspiration ;
but when the discharge is condensed so as to assume
the liquid form, it is called the sensible perspiration.

210. When you breathe upon a looking-glass for a
short time, you observe the glass to become obscured by
the moisture from the breath, which soon accumulates
so as to gather itself into large drops that run down the
glass. This proves that the same process i? going on at

INTERSTITIAL ABSORPTION. 109

all times and very actively, wnthin the cavities of the
body.

211. Now this constant discharge of perspiration
amounts, in twenty-four hours, to a very considerable
quantity. It is a secretion (96,97;) and like all the
other secretions, is furnished from the blood. You can now
comprehend one of the reasons why full-grown animals
require regular supplies of food. This is necessary in order
to replenish the blood continually drained by the secretions.

212. The number and quantity of the various secre-
tions poured out from the body, and therefore taken
from the circulation, is much greater than you might at
first suppose. The tears, the mucus lining all the ali-
mentary canal and many other passages, as well as the
various fluids, such as the saliva, the bile, &c., that are
required to assist in the digestion of food, may be men-
tioned as important secretions; and their formation
demands no inconsiderable supply of nourishment at
all ages to maintain the proper amount of blood.

213. In many fevers, the insensible perspiration is
checked, and all the secretions are very much dimi-
nished in quantity : and this is one reason why the sick
often have no desire for food, and why undue nourish-
ment so frequently renders them worse by forming too
much blood.

214. I must now proceed to explain another much
more wonderful vital operation. If an animal in health
be deprived of its necessary food, the secretions still
continue until the circulation is so far exhausted that it
can no longer supply the wants of life, and the animal
becomes diseased or dies. In fevers, life may be some-
times preserved without food for a greater length of
time than in health, because the quantity of the secre-
tions is then diminished. The loss of the circulating
fluids during partial starvation renders the animal thin-
ner, but it wall not account for the extent to which that
thinness is often carried. A person who is fat at the
commencement of an attack of illness, or a stout man
who is compelled to submit to short allowance at sea,
soon loses his unnecessary fat ; and after a time even

110 rUNCTIONS TRIBUTARY TO NUTRITION.

his muscles, (particularly those of animal life) are gra-
dually diminished in size until they can no longer per-
form their office, and he may become so weak as to be
unable to turn in bed.

215. If deprived of all food, an animal generally dies
before the solid organs of its body are so very much
diminished ; because the exhaustion of the fluids by the
secretion stops the circulation too suddenly. But when
placed in circumstances that enable it to obtain some
food, but not enough, the changes which take place in
the frame-work of the body are very curious. All the
organs are gradually diminished in bulk, but those
which are least important to life are diminished most
rapidly. The heart, for instance, or the alimentary
canal, is rendered feeble, but the muscles of voluntary
motion may almost disappear, and the fat is only to be
seen in a few places where its presence happens to be
essential to the organs in or about which it is formed.
If the slow starvation be carried still further, some of
the le-ss important parts of the body may be entirely
removed. Ulcers break out on the extremities, and some
of the organs that can be spared without the sacrifice of
life are totally destroyed. I have seen most of these
effects produced, in a young man, by a tumour that
pressed upon and finally closed the great canal through
which the chyle flows into the blood (197 :) so that,
although he continued to eat, and for many months par-
tially digested his food, he was as efl^ectually starved as
if he had been inclosed in a dungeon with an allowance
of food diminished every day until nothing was left.

216. Now a moment of consideration will convince
you that the substances that disappear from the body,
wholly or in part, during starvation, must be taken up
by absorption from the organs or parts where they had
been previously placed, and carried out of the body hy
some means. There is no route by which they can thus
be carried out from those animals that hav^e a circula-
tion except through the blood-vessels; and the blood-
vessels have no other efficient means of discharging
them but by the secretions. Hence you see that the

ALTERNATE LIFE AND DEATH OF PARTICLES. Ill

exhaustion of the blood by the secretions, when an
animal is deprived of food, is compensated as long as
possible by the absorption of the less important particles
of the body, which are carried into the circulation by
the lymphatics ; and, perhaps, by imbibition into the veins
themselves (202.) In other words, w^e may say the
starving animal lives for a time upon itself, eating up
by internal absorption such parts of the body as can be
spared under urgent necessity, to feed those organs and
to continue those functions that are absolutely essential
to life.

217. But starvation is not necessary to cause this
constant absorption of particles from the interior of the
body. I have merely selected this very striking example
because you may all observe it for yourselves in the
sick-room, or in persons who are ordered to subsist on
low diet for a long time. The same operation is going
on at all times, even during the highest health. If the
organs of an adult animal in health do not diminish, it
is only because the blood-vessels nourish them with new

fiarticles as fast as the absorbents carry off' the old ones,
f all the organs of a young animal grow stronger with
time, or if the same effect is produced in any particular
muscle by exercise, it is because the blood-vessels, during
youth, deposit more particles in a given time than the
absorbents can take up.

218. It is one of the most curious laws of life, that
there is not a particle in any organized body that can
fulfil its proper functions beyond a certain length of
time. It must then be removed from the body and an-
other deposited in its place by the blood-vessels: so that
in a few years there will not remain in your own person
one atom that now assists in forming your bones,
muscles, brain, or any other portion of your frame !
You will be the same if you Hve, and yet another! for
you will be composed of new materials. It is the im-
mortal part of man alone that preserves the identity of
the individual ! You can be no longer surprised that an
animal w^hose organization is perfected requires nearly
as much food to support that organization as a younger

112 FUNCTIONS TRIBUTARY TO NUTRITION.

one in which many of the organs are still in the act of
growing.

219. As the blood-vessels are the reservoirs into which
all the worn-out particles of the body that are no longer
fitted to fulfil the functions of life are continually poured
by the absorbents, it follows that the blood would be-
come more and more impure by these additions of ex-
hausted matter, until no longer fitted to support the frame,
were not some arrangement made for the ejection of
such materials from the body. This necessary duty is
performed by the secretions.

220. The secretions in animals that have an organi-
zation somewhat complex are very numerous and of
widely different appearance. Thus ; the tears, the bile,
the perspiration, the saliva, &c., are all secretions, and
all contribute to purify the blood ; but they bear httle
resemblance to each other.

221. Why the blood-vessels should secrete tears in
one place, bile in another, and perspiration in a third,
we know not. This is one of the mysteries of life that
so often lead w^eak-minded philosophers to travel beyond
the bounds of human reason in search of first causes, a
journey that always results in the accumulation of a
cargo of uorch instead of things, to be brought home
for no other purpose but to confuse the minds of others,
and deceive ourselves into the belief that we are acquir-
ing a store o( facts, while we are really endeavouring to
hoard up empty sounds. All that we can reasonably ex-
pect to ascertain in relation to the different secretions is
the anatomical structure of the parts by which they are
constructed.

222. So far as the blood-vessels alone are concerned,
there is one po nt of resemblance between all parts of
the body which secrete or separate the secretions from
the blood. The capillaries of such parts are divided,
branched, or multiplied to such an extent that, when filled
with coloured glue, the whole mass often seems at first
sight to be composed altogether of blood-vessels ; for it
will be generally found of a colour almost uniformly red
throughout. Such is the structure of the true skin, and

SECRETORY GLANDS. 113

of the internal lining of the alinnentary and all other
canals that open on the surface of the body ; called the
mucous membranes. The true skin secretes perspira-
tion, and the nnucous membranes throw out the mucus
that lines all such passages, and gives name to these
membranes.

223. Many of the secretions are the work of particular
organs, expressly designed to construct them. They are
called glands, but to distinguish them from another very
curious class of organs belonging to the lymphatic and
lacteal systems, and known by the same general name,
the glands that produce secretions are termed the secre-
tory glands.

224. The secretory glands are as various in structure
as the secretions which it is their function to produce.
In some of them the capillaries are wound or bundled
together like a group of earth-worms in a cup ready for
a fishing excursion : in some, the minutest branches are
arranged in sets more like the teeth of a fine-tooth comb;
while in others, they form beautiful brushes like the rays
of light flowing from a sharp point placed on the prime
conductor of an electrical machine, or the groups of
bristles that form a tooth-brush : but these vessels are
too small to be distinguished by the naked eye, and
it requires the aid of the microscope to render them
visible.

225. The secretions of the secretory glands are gene-
rally poured out by the capillary blood-vessels into a mul-
titude of membranous tubes within the substance of the
glands, often as minute as the vessels themselves ; and
these tubes run together continually, forming trunks
larger and larger until they are collected into one or
more tubes or passages called ducts, which lead the
secretion to the surface of the body or to that of the
alimentary canal. And all these ducts are lined with
mucous membrane, like the other internal passages that
communicate with the surface (212).

226. When we throw^ a very fine coloured fluid with
some force into the blood-vessels of a dead young ani-
mal properly prepared, the fluid can be made to flow

114 FUNCTIONS TRIBUTARY TO NUTRITION.

into the ducts of the secretory glands, and into all the
passages lined with mucous membrane; but the most
careful examination does not detect the slightest com-
munication between the capillaries and the ducts or the
other passages. It appears that the blood in the vessels
is brought extremely near to the ducts or the surface
designed to be bathed by the secretions, but there is
every reason to believe that there is always an astonish-
ingly thin layer of cellular membrane between the blood
and the ducts or the surface. Through this layer the
secreted fluids must pass in order to escape from the
circulation ; and the process by which this passage is
effected is called transjAration ;* a process closely re-
sembling perspiration. This is one of the proofs that
the cellular tissue in the more complex animals exercises
all the functions that distinguish it in the hydra and the
polypi, where it effects all the secretions without the aid
of blood-vessels.

227. It is observed that all the phenomena of nature
give evidence of a beautiful economy ; and this is clearly
exemplified in the history of most of the secretions.
Though these fluids are composed in part, and perhaps
principally, of the worn-out particles of the body (216),
yet nearly all of them are made useful in some way be-
fore they leave the frame entirely. Thus the tears in
man, which are secreted by a small gland within the
bony orbit of the eye, are poured out through six or
more little ducts running down near the outer corner of
the upper eyelid, where they may sometimes be seen by
reverting the eyelid. Here the tears spread themselves
over the eye to prevent friction between the ball and the
lids, w^hich would be extremely irritating to an organ so
delicate. They are then taken up or absorbed by two
other ducts that run from near the inner corner of each
eyelid to a canal leading into the nose, where they assist
in preserving the moisture necessary to the perfection

* Transpiration is a term often used jofenerically, to sig-nify the passage
of fluids or gases tlironrrh metnbranes, internally or externally ; but per-
spiration is a specific term signifying transpiration on to the external sur-
face.

RESPIRATORY APPARATUS. 115

of the sense of smell, and prevent the extreme dryness
of the mucus, that would otherwise result from the
almost continual rush of air through the nose in breath-
ing. Around the mouth there are found several glands
called salivary glands, that secrete the saliva, pouring it
through as many ducts into the mouth. The saliva as-
sists in preventing too much friction from the food in
the act of swallowing, or deglutition. It also assists in
preparing the food for digestion, and probably aids in
producing healthy chyme (193), for we find another
gland, called the pancreas or sweej,-bread, in the inte-
rior of all large animals, which secretes a similar fluid,
and empties it through a duct into the alimentary canal
just below the stomach, where it is mingled with the
chyme as it passes from the latter organ, and before it is
absorbed by the lacteals. The bile is the secretion of the
largest gland in the body, called the liver, of which we
shall have occasion to speak in another part of this
volume. The bile passes through thousands of little
ducts in the interior of the gland until these are col-
lected into one great duct that passes into the alimentary
canal at the same place with the duct of the pancreas.
What part the bile plays in perfecting the chyme we
know not, but there is strong reason to believe that it
acts as the natural purgative, and accelerates the pas-
sage of the food along the alimentary canal.

228. But the most important, and the most universal
of the secretions, is that which is carried on by the or-
gans employed in breathing, or respiration. The func-
tion of respiration is performed by all organized beings.
In plants, the leaves are the breathing organs, and their
office is so important that if all the leaves be plucked or
prevented from growing during the summer while the
vital functions are carried on actively in the stem and
branches of a plant, it will die as certainly as a man
when strangled or confined under water.

229. The principal object of breathing, in animals, is
"to free the body from the w^orn-out particles of one of

the principal substances that compose the animal frame ;
and it may be well to enumerate these substances, in

116 FUNCTIONS TRIBUTARY TO SECRETION.

order that you may better comprehend the nature of
this most interesting function.

230. Besides several metals, sulphur, and phosphorus,
which contribute in small quantities to the formation of
the animal frame, tliere are four diiferent kinds of matter
which, combined in various proportions, compose nearly
the whole mass of every animal. These are, 1st, carboUy
which we see nearly pure in the diamond, and mixed
with but little other matter in common charcoal : 2d,
oxygen, the gas or air that supports the flame of com-
bustible bodies, and gives to common air the power of
maintaining the life 6f animals and plants: 3d, nitrogeriy
a kind of air that will not support life, and extinguishes
a candle when immersed in it, but which forms, when
mixed with a proper portion of oxygen, a considerable
part of the air we breathe ; and, 4th, hydrogen, a gas
that combines with oxygen to form water, and with
carbon to give us the gas that is burned in our streets
in the place of oil. Oil itself owes its inflammable pro-
perties to the presence of this gas.

231. Now, as the four substances above mentioned
(230), combined in different proportions, and rendered
liquid or solid according to circumstances, compose
nearly the whole animal, and as all the particles of all
parts of the animal require to be taken up by absorption
from time to time, to be carried into the circulation and
rejected from the body (216), it follows that the blood,
as it travels through the capillaries in the substance of
the difl^erent organs, must become loaded with these four
substances to such an extent as to require to be con-
tinually purified from them. And as the arteries are
the organs that convey the blood to all parts of the
body in its purer condition, to nourish the frame (186),
while the lymphatics, which empty into the veins, and
the capillary veins themselves (206) receive all the worn-
out particles, it is in the veins that you would expect to
find the blood most in need of purification. The oxygen
and hydrogen are easily discharged from all parts of
the body in the form of water or watery vapour, in the
sensible and insensible perspiration and other secretions.

RESPIRATORY APPARATUS. 117

The nitrogen escapes in many ways without the neces-
sity of any particular organ for separating it from the
blood, but the carbon is not so easily dismissed.

232. It is the presence of an excess of this substance
in the veins of the red-blooded animals that gives to the
blood in the veins its dark purple or bluish tint ; and it
is the removal of the same substance that restores the
bright crimson of the blood always seen in the arteries.
Now a part of the surplus carbon is got rid of in the
liver by the secretion of bile ; but a far greater amount
of purification is demanded for maintaining the vital
functions in health, and special organs are required for
the purpose. These organs, taken collectively, are called
the respiratory apparatus, and the process by which they
perform their functions is called respiration.

233. In order ^o purify the blood of its excess of car-
bon, it is necessary to bring the circulating fluid to the
external air, that its carbon may unite with the oxygen
contained in the atmosphere ; for it is found that wher-
ever the living blood is thus placed, the substances just
mentioned loill unite and form that gas which is known
among chemists by the name of carbonic acid; the
same that escapes from beer, cider, or mineral water.
Wherever a portion of air has been breathed, or sub-
mitted to the action of the respiratory apparatus of an
animal, it is found that a portion of its oxygen has
disappeared, and that a proportional quantity of carbonic
acid gas has taken its place.

234. As many animals live altogether in the water,
and as this fluid contains oxygen as well as air, it is
very commonly supposed that such animals breathe the
water itself. But all water, in its natural state, contains a
large quantity of atmospheric air, which, though we can-
not perceive it, may be extracted by art, as you will
learn when you see it placed upon an air-pump. While
the air-pump is being exhausted, you will observe bubbles
of air continually rising through the water. Now, it is
generally believed by physiologists, that fish and other
animals that live altogether in the water, breathe only
the air that it contains, and not the water itself; and it

10*

118 FUNCTIONS TRIBUTARY TO SECRETION.

is certain that all the experiments yet tried tend to prove
that when water has been artificially deprived of its air.
it can no longer maintain animal life ; so that a fish may-
then be drowned in its own element.

285. You all know that a fish, when taken from the
water, will soon die; proving that too much air will kill
as eflcctually as too little. Thus ; although the birds,
quadrupeds, and man, in breathing, use little else than
the oxygen contained in the air, yet if we enclose an
animal of either of these classes in a vessel of pure
oxygen, he will soon die. You will now readily under-
stand why changes of air, such as those which occur in
moving from the mountains to the sea, from a swampy
to a dry situation, or the reverse, may seriously affect
the health of man and beast, particularly when in a
feeble condition. But this is wandering from the direct
course of our studies.

236. It is not necessary that the blood should actually
touch the external air in order to part with its carbon ;
for this operation takes place through the sides of the
blood-vessels, by imbibition and exhalation or transpira-
tion, like all the organic functions of the polypi and the
hydra.

237. The function of respiration in the simplest ani-
mals is performed by or through the skin ; and even in
many of those which are much more complex in their
organization, some portions of the surface preserve the
same power of action ; but, even in these latter animals,
life cannot be prolonged beyond a definite period without
the aid of a special respiratory apparatus. Thus ; we
know beyond dispute that the toad can breathe through
the skin of the back, and this power no doubt assists in
preserving its life for a long time when shut up in the hol-
lows of trees, or buried in fissures of rock where it can
make no use of its special respiratory organs, and must
depend exclusively upon the air contained in the crevices
of its living tomb, or in the fluids that accidentally trickle
around it. Anecdotes of toads living for months or
years in such situations are not uncommon.

238. There is reason to believe that even man may

RESPIRATORY APPARATUS. 119

breathe, to a certain extent, by his skin ; and different
substances are known to find their way into and out of
the body by this route. Although this kind of respira-
tion is ahogether insufficient for the purposes of an ani-
mal so noble and complex in his organization, the effect
of cleanliness in promoting health and a ruddy com-
plexion is in part due to the removal of all obstacles to
the proper exercise of this function by the human skin.
Many things in the history of wounds and inflammation
tend to establish this fact.

239. But in all animals, except those of the very
simplest character, some definite apparatus is devoted
to the particular purpose of respiration ; and in nearly
all those whose organization in this respect is under-
stood, the most essential part of this apparatus is formed
on one general principle. One or more blood-vessels
are provided, to convey a portion or the v/hole of the
blood to some organ where it may be acted upon by
the atmosphere, or by the air contained in water (234.)
These blood-vessels, though they convey the impure or
venous blood to the purified, appear to be constructed
like an artery. Another vessel, or set of vessels, re-con-
veys the blood, after purification, back to the circula-
tion ; and although these vessels are thus filled with
arterial blood fitted to supply nourishment to the frame,
they are constructed like the veins. It is in the capil-
laries of these vessels and through their sides (236) that
the function of respiration is performed, and the blood
loses its surplus carbon.

240. The capillaries which are expressly devoted to
carrying on the function of respiration are always found
collected together, in such a manner as to form one or
more somewhat irregular organs bearing more or less
resemblance to glands (223,) and generally situated on
opposite sides of the body. In a few animals these pairs
of organs are fixed so near the middle line of the body
that they seem to be united into one.

241. The only important exception to the general prin-
ciple on which is regulated the formation of the respiratory

120 FUNCTIONS TRIBUTARY TO NUTRITION.

apparatus (239,) is found in the insects, certain spiders,
and some kindred tribes that seem not to possess a per-
fect circulation. In the insects, the air is admitted into
the substance of the body through numerous openings
ranged along the side or lower surface of the animal.
These openings are the mouths of as many tubes, which
divide themselves in the interior into many branches
communicating with each other, and bringing the air
almost into contact with the nutritive fluid or blood in
the cellular tissue around their organs. These tubes
are called trachece, and the kind of respiration per-
formed by them is called tracheal respiration. Many
of the worms have also numerous openings to admit air
into small sacs beneath their skin, for the purpose of
respiration ; but I will not saddle your memory with a
description of the endless varieties of the respiratory ap-
paratus of the lower orders of animals.

242. As a general rule, those animals that live en-
tirely in the water have their breathing organs at or
near the surface of the body. These are sometimes in
the form of tufts of hair or prickles that may be useful in
crawling; as in the long red worm so often seen creep-
ing about the hinges of salt oysters. Sometimes they
resemble little paddles or limbs that assist the animal in
swimming; as in a few of the molluscous tribes that
float near the surface of the ocean. But more generally
they are composed of cartilaginous rays, with branches
ranged much like the teeth of a fine-tooth comb, and
covered with a delicate tissue as in the fishes.

243. All respiratory organs designed for breathing
under water, and formed on the models mentioned in
the last paragraph, are termed branchice or gills, how-
ever various their number and shape may be, and
w^hether they are placed altogether externally, or en-
closed in superficial cavities. The kind of respiration
performed by them is called branchial respiration.

244. The different forms of branchiae observed in
aquatic animals are indefinite in number ; but all of them
are furnished with innumerable capillary vessels that

RESPIRATORY APPARATUS. 121

approach so nearly to the surface that they bring the
blood almost into contact with the air contained in the
water, in order to be purified of its carbon,

245. In many of the lower orders of animals, the
branchia hang suspended in the water without any
very apparent apparatus to produce a current towards
them, so that they would seem, at first sight, to depend
for their supplies of air entirely upon the water that
chances to come in contact with them. The common
fresh-water muscle of our brooks and mill-dams will
furnish you with a beautiful example of this kind of
respiratory apparatus. If you open one of these shells
very carefully, you find it lined internally with a soft
membrane called the mantle. Between this mantle and
the tough, muscular, tongue-like organ lying next the
opening, (by means of which the animal pushes himself
along through the mud, and which is therefore termed
the foot,) you see two delicate membranes on each side,
resembling the leaves of a book. These membranes
are the branchiae, and the delicate misty lines which you
may detect ranged like the teeth of a comb along their
margin, are the principal blood-vessels of respiration,
-ivhich the transparency of the animal permits you to
distinguish. As no motion in these branchiae is visible
by the naked eye, you would naturally suppose that the
supply of air that they obtain in still water is very small
and precarious ; but if you long observe one of these
shell-fish in a vessel of water, when undisturbed, you
will see the shell slightly open, and if there be a few
motes in the water, you will soon perceive that there is
a constant current running in at one end of the shell
and out at the other ; thus the branchiae are supplied with
fresh fluid at every moment. The microscope ex-
poses the cause of this mysterious motion ; for it dis-
plays the branchiae covered with innumerable cilia like
those of the polypi, which, by their motion, produce the
current just mentioned (81, 82). When a portion of
one of these membranes is carefully cut ofl^, it is
seen to move about like an independent animal by
the powers of the cilia, and hence many naturalists

122 FUNCTIONS TRIBUTARY TO NUTRITION.

conclude that the latter class of organs are employed as
a respiratory apparatus even by the simplest animals.

240. All animals that live in air are provided with
internal respiratory organs, which are called lungs or
respiratory cavities, and the kind of respiration effected
by these organs is called jmlmonary respiration.

247. The pulmonary cavities are sometimes single,
and formed of a simple sac with an external opening
to admit the air. This is the case with those snails
that breathe in the air only. Many even of those snail-
shells called lymna^oe by naturalists that we find along
the margin of our rivers and streams, living in t"he
water, are provided with organs of this kind. They
would drown if kept continually iminersed ; and if you
observe their habits when preserved in a tumbler of
fresh water, you may see them crawling up the glass at
intervals until they reach the surface and take in a
fresh supply of air. This they do by opening a small
round orifice leading to their pulmonary cavity. When
the air therein has been sufficiently changed, they close
the orifice again, and carry their fresh supply with
them, wherever they travel, until its oxygen is exhausted.
(233). These pulmonary cavities render the animals
much lighter, and assist them in floating upon the surface
in the manner already described (152).

248. The respiratory capillaries in these animals,
instead of being spread over the outside of solid organs,
as in the branchiae, (243) are distributed over the mem-
brane forming the pulmonary cavity, where they bring
the blood nearly into contact with the contained air, —
nothing being placed between the sides of the blood-
vessels and the cavity except an exceedingly thin layer
of the membrane.

249. The pulmonary cavities of the larger animals,
such as the quadrupeds, are constructed upon the same
model ; but instead of a single cavity, these are composed
of a large mass of little cells, collected together like a
bunch of grapes, but clustered in incalculable numbers,
and formed into two large organs, one placed on each
side of the chest, and called the right and left lungs.

RESPIRATORY APPARATUS.

123

Every one of these cells contains air, and the respiratory
capillaries are distributed over their thin walls to purify
the blood.

250. In order to admit the air to the lungs in these
animals, a canal passes from the back part of the
mouth, just behind the tongue, down the neck of the
animal into its chest, where it divides into two great
branches, one of which passes into the left and the
other into the right lung. As soon as these branches
have entered the lungs they are again divided, and
continue to ramify, like the blood-vessels, until they
become exceedingly small, and each of the minute
branches terminates in a group of air-cells. You see a
rude picture of this arrangement in fig. 32.

In fig. 32 you have the left
lung of a man remaining entire,
5, but the right lung has had its
substance and its air-cells cut
away, so as to show you the
large branches of the canal as
they divide within its substance,
7, 7, &c., and a few of the
smaller branches also, 8. Fig.
33 will give you some little idea
of the manner in which the
smaller ramifications, 1, termi-
nate in the air-cells, 2, 2, 2, &c.
The parts are highly magnified;
the air-cells being but barely
visible in the human lungs when
fully distended.

251. The great canal that
passes from the root of the
chest, — fig. 32, 2, — is called
the trachea.* The principal

branches passing to the right and left lungs, are called

* It is perhaps unfortunate that this organ should bear the same name
with the air-passages of insects, although it performs an analogous func-
tion. It would be well for the preceptor to guard the pupil against the
confusion likely to result from this identity of terms.

Trachea and its branches

124 rUNCTIONS TRIBUTARY TO NUTRITION^.

the bronchicB, 3, 4, and the title of bronchial tubes is given
to the various ramifications of the bronchiae in the sub-
stance of the lungs, 7, 7, 8.

Fig. 33.

Air-cells of the Lungs magnified.

1, A minute bronchial tube ; 2, 2, 2, groups of air-cells ;

3, the same parts laid open.

252. If we compare the lungs to a gland intended to
secrete the carbon of the blood, the bronchial tubes,
bronchiae, and trachea may be compared to the ducts of
a secretory gland. Like all such ducts, they are hned
throughout with mucous membrane, but, unlike them,
are never closed or collapsed when emptied of every
thing but air ; for the whole length of the main canal
and its branches, is surrounded by a series of cartila-
ginous arches or rings external to the lining membrane,
which hold it open at all times.

253. The pulmonary respiration of certain shell-fish
(247), requires no machinery for drawing the air into
the respiratory organs and thrusting it out again ; but
the larger bodies of animals whose kings are placed deep
in the body, and who consume a large quantity of air
very rapidly, stand in need of such an apparatus. They
are therefore provided with movable bones in the chest,
called ribs, and numerous muscles for moving those ribs,
which will be more fully noticed hereafter. These
muscles, when in action, alternately raise and depress
the ribs; so as to increase and diminish the size of the
chest and cause the air to rush in and out through the

RESPIRATORY APPARATUS. 125

trachea, to supply the lungs with fresh oxygen, and to
remove the carbonic acid formed in them. The act of
drawing in the air is called inspiration ; and the act of
forcing it out again is callea expiration. These things
you can study on your own person.

254. In birds, it is necessary that the bones should be
very light, in order that they may not embarrass these
animals in flying; and as the laws of Providence are
such that every accidental circumstance connected with
the organization of living things is rendered as useful as
possible, most of the bones of birds are made hollow,
and the air in breathing is admitted into their cavities,
where a great number of capillary blood-vessels are
brought nearly into contact with the air. Thus these
cavities in the bones become a part of the respiratory
apparatus.

255. You know that when the eggs of a frog are
hatched, the young animal appears at first as a tadpole,
residing altogether in the water, and leading the life of
a fish. It is then provided with gills, and has a regular
branchial respiration (243). But after a while its legs
begin to grow, and its tail is diminished in length by
absorption. At this time a pair of true lungs begin to
be found in its chest, and the animal comes often to the
surface to take in air. For a period, it retains both
forms of respiratory organs ; but as the lungs grow
larger, the gills are gradually absorbed, until its respira-
tion becomes entirely pulmonary, if we except its power
of breathing by the skin of the back (237). When the
animal becomes perfectly developed, it maybe drowned
by being kept too long under water.

256. In the great majority of the lower orders of those
animals that have any respiratory organs whatever, only
a small portion and not the whole of the blood is sent
through the branchice or the lungs; so that the arteries are
always filled with a mixed blood, partly pure and partly
impure. The pure blood is that portion which is carried
from the principal blood vessels, through the respiratory
arteries (239), into the branchiae or lungs ; where it
loses its carbon, and is then carried back bv the respira

126 FUNCTIONS TRIBUTARY TO NUTRITION.

tory veins into the principal blood-vessels again. The
impure blood is that which passes directly along the
principal blood-vessels from the arteries to the veins,
without passing through the respiratory organs at all.

257. Now, it is found that all the vital functions are
performed most vigorously in those animals whose arte-
ries circulate the purest blood ; and hence those beings
alluded to in the last paragraph are remarkable for the
sluggishness of their motions and functions, and for
their power of retaining life for some time without air.
Snakes, tortoises, and lizards, which are amphibious,
are of this class; and so are a multitude of still less
complex animals.

258. But in man, quadrupeds, and birds, all the blood
in the veins is made to pass through the lungs before it
recommences its route through the circulation; so that
the various parts of the body are supplied exclusively
with pure blood from the arteries. It is this circum-
stance that renders these animals so rapid and powerful
in their motions, and enables them to display so much
activity of all the vital functions, while, at the same
time, it makes them more dependent upon the good
quality and ample supply of air for breathing.

259. I shall not attempt to describe, in this work, the
forces that compel the blood to flow through the vessels,
or the various forms that the heart assumes in different
animals ; for you will be much better prepared to read
understandingly on these matters hereafter. But it is
necessary that I should give you some definitions of
terms connected with circulation and respiration that we
may shortly have occasion to employ. As, in the most
perfect animals, the respiratory arteries carry only impure
blood in order that it may be purified in their capillaries,
they cannot properly support the growth and nutrition of
the respiratory organs themselves. These organs are
therefore supplied with another and much smaller set of
arteries springing from some of the principal arterial
trunks carrying pure blood. The arteries of this small
set nourish the respiratory organs, but have nothing to
do directly with the function of respiration. They are

STRUCTURE OF THE HEART.

127

called the nutritive arteries of the lungs or hranchice.
Both the respiratory and the nutritive arteries have
their corresponding veins, to carry back the blood that
they have conveyed into the respiratory organs. Those
attached to the former system deliver their pure contents
into the great arteries that nourish the whole frame, but
those of the latter system deliver their impure contents
into the principal veins that bring back the blood from
all parts of the body to be purified. Thus you see that
the nutritive system of vessels is completely distinct
from the respiratory system, even in the respiratory
organs themselves. The respiratory system of blood-
vessels is called branchial when the animal breathes by
gills, and pulmonary when it is furnished with lungs :
b»» these terms are not applied to nutritive vessels.

Fig. 34.

The Heart in the Pericardium.

128

FurrcTiONs tributary to nutrition.

260. To distinguish the respiratory system of vessels
from that which conveys nourishment to all the organs,
it has been customary to call the latter the systematic
circulatory apparatus; but having objected to the term
system, as applied to the ichole body (25), because it is
likely to confuse the mind when thus employed, I prefer
the term general or nutritive system to designate this
class of vessels.

261. It is now time to give you some idea of the func-
tions of the heart in carrying on the circulation of blood
in all the vessels of the larger animals and man. At
fig. 34 you see a representation of the human heart in-
closed in a thin membrane that covers it like a bag, and
surrounded by the large blood-vessels that spring from

Fig, 35.

It. At fig. 35 you see the human
heart divided from side to side, so
as to show that it contains the
four different cavities marked with
the numbers 3, 4, 10, and 1 1 . You
see a solid division running down
the middle of the organ, marked
6, separating the two cavities on
the right from those on the left ;
and it is necessary for you to re-
member that you are looking at
the organ as it would appear if
the individual to whom it belonged
were facing you, so that the left
side of the heart is next your right hand. This division
between the two sides of the heart in the larger animals
and man is always complete after birth, except in some
rare cases of disease ; so that no blood can pass from
the cavities marked 3, 4, to those marked 10, 11. But
between the cavities marked 10 and 11 there is a division,
5, that is not complete. It is composed partly of thick
muscular and tendinous matter, like 6, but there is a
large opening in its centre which is furnished with a
valve composed of a thin membrane that lines not only
the heart, but also the whole length of the arteries. This
valve is scolloped so as to form three festoons, each oc-

The Heart seen in Section

STRUCTURE OF THE HEART. 129

cupying about one-third of the circumference of the
opening, with their loose edges hanging down a little
toward the cavity marked 11. When the cavity 10 is
full of blood, this fluid can pass easily into cavity 11 by
pushing open these festoons; but when it attempts to re-
turn it arrests itself at once by forcing the festoons against
each other so as to close the passage. To guard against
the valve being driven upward through the opening by
a sudden rush of blood, the loose edges of the festoons
are secured by a number of little tendons arising from
columns of muscular fibres springing from the sides of
cavity 11. These tendons prevent the festoons from
rising so high as to be inverted upward, which would
destroy their usefulness. Between cavities 3 and 4
there is a valve, also marked 5, similar in all respects,
except that it is scolloped into only two festoons.

262. The cavities marked 10 and 3 are called the
right and left auricles. They receive all the blood brought
to the heart by the veins of the two systems, the gene-
ral and the respiratory (259, 260) ; and, when full, they
contract and force it through the. two valves, 5, 5, into
the cavities 11 and 4. These latter cavities are called
the right and left ventricles. All the arteries in the body,
both general and respiratory, spring from these ventri-
cles by two great trunks, each of which continues di-
viding again and again until its ramifications form the
capillaries in the manner already described (186, 187).
Now, when the ventricles contract, the blood that they
have received from the auricles endeavours to flow back
into those cavities, but it is immediately stopped by the
closure of the valves (261) ; and it is therefore forced
into the arteries, which furnish the only outlet. The two
great arteries are also provided wdth valves at their
origin where they leave the heart ; so that the blood that
has once entered them cannot flow back into the ventri-
cles, but must flow forward into the capillaries, and thus
into the veins, before it can return to the heart. These
are the only valves seen in the arterial system. Although
the great veins near the heart are not provided with
valves, the smaller ones which unite to form them have
11 -^

130 FUNCTIONS TRIBUTARY TO NUTRITION.

very numerous valves; as you have been informed alrea-
dy (see fig. 29, page 97) ; and this will explain why the
auricles, when they contract, do not force their contents
back into those vessels. Thus you perceive that the blood
is compelled to move regularly in one direction, or to fol-
low one fixed route of circulation. Let us trace that route.

263. All the veins from the head, neck, and upper ex-
tremities, before they reach the heart, form one great
venous trunk called the superior or descending vena cava,
fig. 35, 1; and all the veins coming from the body and
lower extremities form a similar trunk called the inferior
or ascending vena cava, 2. These two great vessels,
filled with the dark-coloured or impure blood (232), meet
together just behind the heart, so as to resemble but one
continued vein. (See fig. 28, page 96.) At this point they
communicate directly by means of a large opening in
their side, with the right auricle of the heart, 10, fig. 35 ;
into which they empty their contents.

264. At every beat of the heart the right auricle con-
tracts and forces its contents into the right ventricle, 11.
This ventricle then immediately contracts and drives
the blood into the great arterial trunk that arises from
it (262), which is called the pulmonary artery, 7. This
artery soon divides, as you see at 8, into a right branch
going to the right lung, and a left branch going to the
left lung. The two branches of the pulmonary artery
convey the impure blood into the lungs, and there distri-
bute it to the pulmonary capillaries, which separate its
carbon in the manner already described (239), and ren-
der it fit to support and nourish the frame. The pure
or bright red blood thus formed then passes from the
pulmonary capillaries into the minute branches of the
pulmonary veins, which, as they travel toward the heart,
unite continually with each other until they form four
large trunks called the pulmonary veiiis, 9, 9. These
branches all pour their contents into the left auricle of
the heart, 3; and this forces the blood into the left ven-
tricle, 4. When this ventricle contracts, its contents are
driven into the great arterial trunk that arises from it,
which is called the aorta, 12. The aorta is the crreat ves-

STRUCTURE OF THE HEART. 131

sel that supplies all the frame with support and nourish-
ment. It conveys the pure blood into the general or
nutritive capillaries of all the organs and into those that
furnish all the secretions. From these capillaries the
blood passes into the minute veins of the nutritive sys-
tem, which finally unite continually into trunks becoming
larger and longer until they form the two venae cavas with
which I commenced this description. Such is the route
of the circulation. The aorta and its branches form the
great arterial system seen in fig. 30, page 98.

265. You perceive, then, that the right side of the heart,
together with all the veins leading towards it, and the ar-
teries leading from it, are filled with the dark, impure or
venous blood, and the left side with its vessels contains
the pure, bright, or arterial blood. The substance of the
heart itself is nourished by two arteries that branch oflf
from the commencement of the aorta, and their capilla-
ries pour the blood into the minute branches of veins that
finally empty their contents into the right auricle.

266. The total separation of the sides of the heart
from each other by the partition 6, Fig. 35, has led some
physiologists to speak of them as two hearts associated
together ; thus we hear of the right heart and the left
heart; and it is a curious circumstance that in the
dugong there are actually two well-formed hearts merely
united together at their upper or thicker parts, each
containing but one auricle and one ventricle. But if we
begin to view the heart as more than one organ, we
may consider it as four distinct machines with as much
propriety as two ; for some of the inferior animals ac-
tually have the auricles and ventricles widely separated
from each other, with long vessels to convey the blood
from one to another.

267. The right ventricle is commonly called the pul-
monary ventricle, because it sends the blood to the lungs ;
and the left auricle is called the pulmonary auricle, be-
cause it receives the blood from the lungs. For the same
reason the left ventricle and the right auricle are often
termed systematic, because the former propels, the blood
to all the organs, and the latter receives it from them.

132 FUNCTIONS TraBUTARY TO NUTRITION.

Hence you will find that till the physiologists speak of a
" double circulation," — " a pulmonary circulation and a
systematic circulation" — in the more perfect animals and
man. Now all these terms are calculated to mislead
the learner, and are not founded in fact. There is hut
one circulation, during which the blood passes from the
right side of the heart, first through the pulmonary ves-
sels, next through the left side of the heart, and, lastly,
through the nutritive vessels back to the right side of the
heart again. But it is convenient and proper to speak
of the respiratory or pulmonary circulatory apparatus and
the general or nutritive circulatory apparatus ; the former
of which is composed, in the larger animals, of the right
ventricle, the pulmonary artery, the pulmonary veins, and
the left auricle, while the latter is formed b}^ the left
ventricle, the aorta with its branches, the venae cavae
with their branches, and the right auricle. By becoming
familiar with these terms, you will be able to compre-
hend all that you will read of the circulation and respi-
ration here or elsewhere.

268. The capillary blood-vessels of the general circu-
latory apparatus — or the general or nutritive capillaries —
are distributed in countless numbers throughout the
various organs of the body ; and they not only branch
out in various directions, but the branches from different
arteries unite with each other so as to form a complete
network. Were it not for this arrangement, every sur-
gical operation requiring that an artery should be tied,
and every accident causing a division of one of these
blood-vessels, would be followed by the death of all the
parts of the. body supplied by that vessel. But in cases
of this kind the blood flows easily, through the capilla-
ries arising from the surrounding uninjured arteries,
from one part of the divided trunk to the other ; and thus
the current is continued. Ev^en the larger arteries often
communicate in this way in particular situations, and
the veins are still more remarkable for their frequent
connexion with each other, as you may observe on
examining those seen on the back of your hand and
wrist. These junctions are called anastomoses. Almost

UNEQUAL DISTRIBUTION OF VESSELS. 133

any one blood-vessel in the body, except the aorta
before it sends off its first great branches, or the venae
cavae just before they reach the heart, may be slowly
obliterated by disease without producing death, because
the circulation will still find other routes through the anas-
tomoses between the capillaries of the branches given
off above and below the obstruction respectively ; and
these new channels will slowly enlarge themselves until
they allow ample room for the current of blood.

269. But when a large artery is tied suddenly, there
is great danger of mortification or local death in the
parts nourished by it ; and if all the blood-vessels of either
class that communicate with an organ or member be
obstructed, mortification inevitabl}^ occurs in a few
hours.

270. The life of a part being thus dependent upon the
supply of blood that it receives, you will not be surprised
to learn that those organs whose vital functions are very
active receive the largest supply of capillaries ; — that
all the organs of a young and growing animal have
proportionally larger blood-vessels than those of adults,
whose frame is already completed. Hence it is easy to
understand why the young require more food than older
persons, and why that food must be taken more frequently,
in order to insure health.

271. The muscles receive a much larger amount of
blood than the tendons or ligaments ; because the former
are active organs, while the latter are merely passive.
The more the muscles are employed, provided they be
not strained and weakened by over-exertion, the larger
and stronger they grow ; because the more rapid is
the flow of blood towards them, and consequently the
greater is the quantity ofnourishment they receive. Partly
to supply this additional nourishment, the heart is made
to beat more rapidly while we use exercise, so as to hasten
the circulation. Now, the more active the employment
of any organ is, the faster its particles are worn out,
and the more quickly they must be removed by absorp-
tion and carried into the veins to make room for fresh
particles from the blood. This is the reason why

1^4 CAUSES DISTURBING NUTRITION.

we breathe more rapidly during exercise, to purify the
blood of its carbon as fast as it becomes impure.

272. If we could examine a muscle while in action,
we should always find its capillaries enlarged and much
more full of blood than usual ; and if industry call it into
habitual exertion, the capillaries become permanently
enlarged ; which circumstance accounts for the lasting
strength resulting from well regulated labour.

273. If any set of muscles be kept permanently at
rest, they gradually lose their strength ; for the capil-
laries then become smaller and smaller, because little
blood is called into them. The absorbents take up the
old particles faster than the arteries deposit the new ones;
and the organs are rendered thinner continually until, in
extreme cases, the muscular structure nearly disappears,
and the parts are reduced almost to the condition of
simple cellular tissue : — a condition of things sometimes
seen in old cases of palsy. This is found to be the case
in those Hindoo devotees who make vows to hold an
arm or a leg in a particular position without changing
it for years. The muscles that should move such mem-
bers are found after a time to have lost all power of
contraction. I have seen a lunatic who sat crouched in
the corner of his cell, during several years, without ever
assuming the erect position. At last, on one occasion,
a brother lunatic roused his anger to such a pitch, that
he made every effort to rise and give him battle ; but it
was too late : he had lost the power of the muscles that
enable us to stand !

274. What has been said of the effects of exercise on
the muscles is true of all the other organs. When their
functions are rapidly and energetically carried on, there
is the same rush of blood to the part, and the same
enlargement of the capillaries. Increased strength
and developement follow in like manner from their
properly regulated exertion, and weakness and wasting
are as certainly produced by suffering them to remain
too long inactive. Digestion is the proper exercise of
the stomach, and you can now understand why the heart
beats more quickly soon after a hearty meal, producing

EXERCISE AND REST. 135

the symptoms of a slight fever. Nor is it more difficult to
account for the weakness of stomach that results, espe-
cially in childhood, from a deficient supply of food, or
from eating that which is of an unwholesome quafity.
The brain is universally acknowledged to be that part
of the organized being which excites consciousness and
receives immediately the mandates of the will, in all
those animals that have a brain, and thinking and willing
furnish it with its proper exercise. Whenever the mind
is occupied, an additional flow of blood is known to be
thrown into the brain ; and so powerfully does this tend
to increase the action of the heart, that it is of the utmost
importance to avoid all strong excitement of mind during
fevers, and in persons whose health is delicate. By the
proper exercise of the mind, the brain is made to increase
in size and power ; — by long continued idleness, it be-
comes feeble, and even dwindles in hulk. How import-
ant is it, then, that we should rightly employ the powers
that Providence has bestowed upon us, in order that we
may strengthen and increase them ! No function can be
permanently neglected without subjecting us to a punish-
ment proportionate to the importance of the idle organ.
275. Although tlie habitual exercise of the function of
an organ increases its bulk and strength, and its long
continued repose diminishes them, you should not infer
that perpetual activity promotes the nutrition of any
part. Alternate rest and exertion are necessary to the
health of all the organs. Even the heart, though it keeps
up a continual circulation, enjoys its period of rest at
every pulsation, and it is allowed to do so in the follow-
ing manner. The right auricle receives its blood from
the vense cavte at the same moment that the left auricle
receives its portion from the pulmonary veins; and dur-
ing this operation the auricles are relaxed so as to rest
themselves from all exertion. At the same moment that
these cavities are becoming filled, the two ventricles are
in the act of contracting and expelling their contents
into the arteries. The instant the latter are emptied,
they relax themselves in their turn, and the auricles con-
tract and drive the blood into them. Thus, one half the

136 CAUSES DISTURBING NUTRITION.

heart is-^lways resting while the other half is in action.
This is the cause of the double beat that is felt when one
places a hand on the heart.

276. When, on long pedestrian journeys, a man exerts
himself to great excess in walking, he is observed to grow
thinner from day to day, instead of increasing in bulk ;
because the power of life is mainly directed to his mus-
cles, and his stomach will not act with energy in digest-
ing his food except when they are at rest. If he at-
tempts to eat while using great exertion, or if he uses
powerful exercise immediately after a meal, his stomach
refuses to digest, and the food, instead of supplying nour-
ishment, becomes altered in character and irritates the
organ ; so that if he desires to be able to continue his
labour or his journey free from dyspepsia or other dis-
ease, he must take his meals when he has sufficient
time to repose his muscles. As this happens but seldom
during pedestrian excursions, he is obliged to live the
greater part of the time upon himself (216) which is a
sufficient reason for the thinness observed on such occa-
sions. A wise traveller, if he be charitable or even
economical, will attend to those circumstances that dis-
turb nutrition at its fountain head — the stomach — not
only in his own person, but even in his horse. Fortu-
nately, violent exercise, while it lasts, diminishes the ap-
petite— but after it is over, both the appetite and the
rapidit}^ of general nutrition are astonishingly increased.
After long journeys both men and horses who have fol-
lowed a well-regulated course of diet and exertion grow
fat and fleshy with surprising speed.

277. Sleep is the natural repose of all the organs. It
is perfect in some, but partial in others. When we do
not dream, our voluntary muscles and our minds are per-
fectly at rest; even the tonicity of all the fibres is diminish-
ed (116); and although the stomach still acts, if it con-
tains food, it acts feebly and laboriously, and suffers in
consequence. Hence the unwholesomeness of late sup-
pers, which are very apt to arouse both the mind and
the muscles, in dreams, at the same time thar they ex-
haust the stomach. The nutrition of the organs, absorp-

OVER EXERTION — SLEEP. 137

tion, and secretion continue during sleep, but they are
much less active. Even the heart beats more slowly,
and the pulse and breathing are less frequent. You can
readily understand, then, how seriously the loss of a pro-
per proportion of sleep must affect the health of animals ;
for it not only disturbs nutrition by exhausting all the
organs by which that process is effected, but it fatigues
also the muscles and the brain. Muscular and general
debility, weakness of mind, and even insanity, may be
produced by it. The more all the organs of the body
are employed, the more repose they require ; and as the
organs of a child are busy with their own growth, in
addition to their proper functions, a child requires much
more sleep than an adult. In old age, as you will learn
presently, the nutrition of the body becomes less active,
and all the apparatus of nutrition — the stomach, lacteals,
heart, and blood-vessels — move more slowly. In addi-
tion to this, the muscles become feeble, and are less em-
ployed. Hence old persons require much less sleep than
even those in middle life. Cruel suffering and loss of
health to children and servants often result from an igno-
rance of this principle ; but let not this fact be advanced
as an apology for improper indulgence ; for an excess
of sleep is sure to produce feebleness of mind and body
by preventing the proper exercise of the functions.

278. An exertion of any organ beyond its powers
induces weakness that disturbs the nutrition of the organ
for a considerable time ; and it recovers its energy more
slowly in proportion to the excess of its exertion. When
this is extremely violent, the function of the organ may
be totally and permanently destroyed. We sometimes
see palsy produced in a muscle, simply by the effort to
raise too great a weight. The sight is impaired, and
total blindness may be produced by exposure to a
light too strong or too constant. The mind may be de-
ranged, or idiocy may follow the excess of study or the
overtasking of the brain. I have actually witnessed all
these results and many others of a similar character.
Now when the function of an organ is permanently im-
paired or destroyed by over exertion, the nutrition of

188 CAUSES DISTURBING NUTRITION.

the part is rendered insufficient, or is entirely arrested ;
and then the absorbents remove it wholly or partially, as
they do every thing that is no longer useful. Thus, in
palsied patients, a few years after the attack, we often
find scarce any trace of the palsied muscles remaining ;
they are reduced almost to simple cellular tissue. The
condition of the calf of the leg in persons with club-
foot is a familiar proof of this.

279. In some countries, and in some professions, mul-
titudes of unfortunate children or slaves are compelled
to labour daily without sufficient food or sleep, and with
scarce any rest after their meals. These miserable
beings are also deprived of proper exercises for the
mind, while their voluntary muscles are continually
overtasked. Can you wonder, then, that all these causes
of disturbance to nutrition should render them feeble,
sickly, often deformed, and generally imbecile ? Such
cases are yet rare in our happy country ; but the time
is fast approaching when the ignorance of physiological
laws in masters and employers, together with the in-
creasing demands of luxury and avarice in a crowded
population, must render them common. May I not hope
that your reflections upon the general principles here
laid down will render you useful in checking such hor-
rors when your age and social position shall have ex-
tended your sphere of influence?

280. The process of assimilation (47,48), — com.menced
in the alimentary canal by the formation of the chyme,
continued in (he lacteals by the perfection of the chyle.
and still further perfected in the lungs when the chyle is
carried into them mingled with the venous blood* (197) —
is not brought to perfection until the particles selected from

* W^e know not what chang-e is produced in the chyle by respiration
after it has mingled with the blood in the veins of the g-eneral circulatory
system and has been driven with that fluid into the respiratory organs ;
but we do know that it can be tracec^. no farther than the pulmonary
capillaries. It is not to be found in ihe arterial blood. Some physiolo-
gi.sts believe that more oxygen is absorbed in the lungs than is necessary
to form the carbonic acid that is expired. If so, this surplus oxygen
may be united with the chyle to convert it into arterial blood. But this
subject has not been sufficiently examined.

NECESSITY FOR A NERVOUS SYSTEM. 139

the blood are actually combined with the substance of
the body which they are designed to nourish. Now,
you have been told that each organ has its peculiar
mode of life, and selects for itself the particles necessary
for its growth and sustenance. The organs themselves
are therefore to be regarded as agents in effecting the
nutrition of the frame, and it is in them that the process
of assimilation is completed.

CHAPTER VIII.

ON" THE NERVOUS SYSTEM.

281. You have now made sufficient progress in your
studies to perceive how various and complex are many
of the motions necessary to maintain the hfe of an ani-
mal of an elevated rank in the scale of nature. You
have seen this very strongly exemplified in the history
of nutrition, for the accomplishment of which func-
tion the ahmentary canal is called into action in order
to digest the food, and to pass the chyme forwards so
as to be gradually subjected to absorption; the lacteals,
to convey the chyle to the blood-vessels ; the right side
of the heart, to drive it into the respiratory organs ; the
respiratory organs, to convert it into arterial blood ; the
left side of the heart to drive this blood through the
aorta, &c. ; and finally, the various organs themselves
come into play in order that each may select from the
blood the sustenance that it requires. Nutrition being
once completed, absorption soon commences; the lym-
phatics and the veins convey the worn-out particles of
the frame back into the circulation ; and the respiratory
organs and secretory glands begin the process of puri-
fication, that the breath and the ducts of the glands may
discharge from the body the particles that are unfit for
the purposes of life. These complex motions cannot be
performed in an irregular manner. They must succeed

140 THE NERVOUS SYSTEM.

sach other in proper order in propelling every particle
to its proper destination, or life would be sacrificed in
the more complex classes of animals, almost at the
moment of its commencement. There is therefore a
mutual dependence of all portions of the machinery of
organic life (101) upon each other, and a necessity for
some medium of communication from one organ to
another by which they may convey mutual information of
their several conditions, if I may be permitted to employ
a figurative expression. Were there no such medium,
how would the stomach notify the heart that additional
exertion on its part is required, because the stomach is
busy in digesting food (-74) ? When w^e are exerting
our muscles for a long time together in some laborious
employment, how else are our members to inform the
stomach that they are too much occupied with their
duties to spare the blood necessary in digestion, that it
is requisite that the appetite should decline, and that
digestion should cease for the time, even if the stomach
should be oppressed with its contents (276) ? When we
are thinking, how else are the blood-vessels to be told
that an unusual supply of their contents is wanting in
the head (274)? or when the whole frame is weary
with exertion, how, without some regular line of intelli-
gence between the various organs, is the brain to be
instructed that circumstances require that it should go
to sleep (277) ? To supply the necessary medium of
communication. Providence has furnished all the animals
that possess distinct organs with a peculiar apparatus
called the nervous system.

282. In the simplest animals, that are not provided
with any obvious organs, we discover nothing resem-
bling the nerves : but even in the most minute and
apparently unimportant beings that have any trace of a
circulation or muscular system, something like the rudi-
ments of a nervous system are perceptible. At first we
detect nothing of the kind except a few faint white lines
runninn; from one orjran to another throuo-h the trans-
parent substance of which these animals are formisd :
and it is only among such as are a little more elevated

MEDULLARY AND CINEIllTIOUS MATTER. 141

in the scale of nature that we can usefully study the
structure of this singular system. It is best understood
from an examination of the anatom.y of the quadrupeds
and man ; and when we speak of the materials that
compose the nerves in those animals that have no
internal skeleton, we are compelled sometimes to reason
from analogy rather than from actual observation.

283. Thus examined, the matter constituting the ner-
vous system appears to be composed of two substances
very strongly resembling ea^h other, but differing in
colour and in the arrangement of the particles. The
first of these substances is called the cineritious matter of
the nervous system, from its colour, which is ash-gray
or reddish. When examined under the microscope, it
appears to be formed of minute globules collected
together without any particular order. The second is
called medullary matter. It is of a clear white or
pearly colour, and the globules of which it is composed
seem to be ranged in regular rows so as to form fibres
or filaments of great length and extreme delicacy.

284. In those animals that are provided with a brain,
properly so called, — that is, in all animals that have an
internal skeleton, — this most important part of the frame
is composed of a large amount of both these substances,
penetrated by innumerable minute capillaries ; as are all
the organs in the body, except, perhaps, the articular
cartilages. The cineritious matter is placed, for the
most part, on the outer surface of the brain, whence it
is often called cortical substance, and the central por-
tions are chiefly composed of medullary matter. It is
observed that every filament of this medullary matter
originates at one extremity in the cineritious or cortical
substance, and the latter owes its red colour to the greater
size and number of its capillaries.

285. The cellular tissue in which the cineritious and
medullary matter are deposited is so extremely delicate
that it cannot be delected during health; and its exist-
ence has been denied by some physiologists, who have
considered the nervous system as an apparatus con-
structed on different principles from the other organs of

12*

142 THE NERVOUS SYSTEM.

the body ; but in certain diseased conditions, the cellular
membrane of the brain becomes very distinct. Some
cavillers insist that in these cases the membrane is
formed by the disease, and does not exist in the healthy
brain ; but I have recently met an instance in which it
was so thickened and hardened in one spot by an injury
of the head, that several ounces of cortical and medullary
matter were seen completely enclosed in distinct cellular
tissue as strong as that which surrounds and penetrates
the muscles (149) : thus giving undeniable proof of the
beautiful simplicity of the natural laws that govern the
formation of all organized bodies without exception.

286. The consistence of the nervous matter of the
brain is scarcely greater than that of curdled cream or
the softest cream-cheese, but it is always enclosed in a
bony case that protects its most delicate structure from
injury.

287. Besides the brain, there are many other collec-
tions of medullary and cineritious matter formed into
small masses, and scattered throughout the body. These
are called ganglia, and each ganglion is considered by
some physiologists as a little independent brain, ruling
over some of the organs in the same manner that the
true brain seems to do over the frame in general.

288. The brain and ganglia are two most important
parts of the nervous system, and each little row of
globules of medullary matter which they contain (283),
may be regarded as a nervous filament; yet these
organs are not commonly called nerves; that name being
reserved for another portion of the system which will be
presently described: they are often called nervous centres.
At one extremity, each of the nerves in the body is con-
nected either with the brain or a ganglion, from whence
it runs to be distributed to some distant part. It is the
special function of each of the nervous centres to receive
information by means of certain nerves, of what is pass-
ing in that portion of the frame over which it presides,
and to issue through certain other nerves, the orders
necessary to regulate the action of all the organs of the
body accordingly.

NERVOUS FILAMENTS AND TRUNKS. 143

289. A nerve is a bundle of medullary filaments (283)
collected into a cord passing from the brain or from a
ganglion to some distant portion of the body, the func-
tions of which are subject to its control. At fig. 36 you
see the representation of

a portion of a very large Fig» 36.

nerve with its fibres or
filaments, one of which
has been drawn out by

a pin. The whole cord a portion of nerve.

is always covered by a

strong sheath of cellular tissue strengthened with fibres,
forming a membrane called the neurilema or nervous
coat, which would resemble a tube were all the fila-
ments removed ; and each particular fibre is enclosed
in an extremely delicate sheath of the same kind of
membrane. In this respect the nerves are arranged
like the muscles (146). In fig. 36, the thick membranous
covering conceals the filaments, so that their divided
extremities alone are visible.

290. Each nervous filament has its own especial des-
tination, and is believed not to be united w^ith other fila-
ments in any part of its course. It has also its own
peculiar function, and may act independently of those
with which it is associated. A nerve is, therefore, a
bundle of organs rather than a single organ.

291. In the primary nervous trunks, where they first
come out from the substance of the nervous centres, all
the filaments appear to possess similar, though not per-
fectly identical functioHs. Thus, one cord is composed
of filaments, all of which are acutely sensitive to the
touch, while another employs all its fibres in controlling
the motions of the parts to which it is distributed. If
you divide the former, you destroy all sensation or feel-
ing in the part to which the nerve is distributed, though
its motions may continue. Thus we see certain cases
of palsy, in which the patient cannot feel the slightest
pain in an arm or a leg when pricked by a pin or
injured in any other way, and yet he continues to use
the member as when in health. If, on the contrary, we

144

TIIK NERVOUS SYSTEM.

divide one of tlie latter class of trunks, all power of
motion ceases in the parts supplied by it, but the sensa-
tion or feeling remains. Thus, there are cases in which
the limbs are palsied and rendered totally useless, yet
continue to feel, and may even be the seat of severe
pain induced by disease. You must divide or injure
both trunks, or the filaments arising Irom them, before
3'ou can destroy the function* of both muscular motion
and feeling.

292. But few of the nervous trunks travel far from
their origin in the nervous centre to which they belong
before they send oft' some filaments to associate them-
selves with other trunks whose functions are of a dif-
ferent character from their own. From the combination
of these ditlerent sets of fibres new^ nervous cords are
formed. Each fibre of these compound cords retains
the same function that it exercised in the parent or
original trunk to which it previously belonged, but the
whole nerve, resulting from the assemblage of fibres
from different sources, enjoys all the functions of the
difterent trunks that send branches to assist in forming
it. As one of these secondary nerves approaches the
parts with w^hich it is designed to communicate, it
transmits to them branches or bundles of fibres, most

of which contain fila-
ments from all the
parent trunks, but at
length these filaments
are separated from
each other, and each
conveys to its final
destination the same
powers that it pos-
^ sessed when it first
left its nervous cen-
tre. Let me give you
an example. In fig,
37 you see a repre-
sentation of the ori-
gin of four of lliG

Origin of Bpiiial Nerves.

PLEXUS OF NERVES.

145

nerves of feeling, and four of the nerves of motion in
man: these all originate from the spinal marrow — a
nervous centre closely associated with the brain, and
occupying a canal formed by the bones of the back, as
will be explained in the after part of this volume : a is
the spinal marrow ; J\ the membranes lining the canal
in which it is placed ; h is the original trunk of a nerve
of feeling, commencing from the spinal marrow by many
little bundles of filaments with similar functions, and
united into one cord at d. If you cut this cord, all
feeling will be instantly destroyed in those parts of the
body to which these filaments are distributed, but the
power of muscular motion will remain. At c, is seen
the original trunk of the nerve of motion, designed to
supply the same parts of the body. It originates from
the spinal marrow in a similar manner, and its filaments
are also collected into one cord at c. If you divide it,
all power of muscular motion in the parts supplied by
its filaments is immediately lost, but feeling still contin-
ues. All the filaments from both these original trunks
are soon collected into one bundle instead of two, so as
to form a single resulting nerve, e, that commands both
motion and feeling — if, then, you divide this compound
nerve, both feeling and motion must cease in all the parts
to which a fibre ofeither of the original trunks is distributed.

293. It is not uncommon
for a considerable number
of nerves to intermingle
their branches, so as to
form a nervous network,
giving rise to a number
of new cords, or distinct
nerves ; so that the original
trunks from which the fila-
ments are derived seem to
be lost in the labyrinth into
which they are thrown.
Such a network is called a
plexus, and one of these is
represented at fig. 38, You

Fig. 38.

A Nervous Plexus.

146 THE NERVOUS SYSTEM.

can readily judge how complex the function of a nerve
originating from a plexus may be rendered ; but each
fibre generally retains its own powers unaltered ; and the
plexus cannot be regarded as a proper nervous centre.

294. The ganglia or true nervous centres are scat-
tered throughout many parts of the nervous system, and
generally they appear as if formed by the enlargement
of one or more nerves, which do not appear to termi-
nate in them, but pass through them on their way to
their ultimate destination. The number of nervous
trunks that enter a ganglion on one side is often less
than the number that pass out on the other ; but the
latter, taken collectively, are almost always larger than
the former. This seems to show that some matter must
be added to the nerves as they pass the ganglia.

295. It is believed that all the filaments of the original
trunks entering these organs continue their route without
interruption to the resulting branches that leave them.
But their filaments, while within the ganglion, are de-
prived of their cellular sheath or neurilema (289), so
that they are reduced to nearly the same condition with
the fibres of the brain (288), and are brought into con-
tact with the cineritious matter that forms part of the
bulk of a true ganglion. The filaments are wound
round each other in the most complex manner ; so that
they are traced with extreme difficulty ; but it is believed
that every nerve passing out of a ganglion contains
fibres derived from each of the trunks that enter it.

296. The interminsjlin"; of the nervous matter in the
ganglion is much more intimate than that which takes
place in the plexus ; and the very functions of the fila-
ments seem to be changed or modified by this close
association. It is also believed that new fibres origi-
nating from the cineritious matter of the ganglion are
added to each resulting nerve.

297. You have learned, in the earhest part of this
work, the following facts: 1st, That the simplest ani-
mals, apparently composed of cellular tissue alone, and
unprovided with any special organs, are capable of
digesting their food without any special organs of di-

DISTRIBUTION Or NERVES. 147

gestioD : but that animals of more complex organization
require a peculiar apparatus to accomplish the same func-
tion. You have learned also that the former animals
can drive their nutritive fluid, or blood, from place to
place, so as to nourish all the parts of their frame, by the
mere contraction of the cellular tissue ; but that the lat-
ter have need of a circulatory apparatus, and capillary
vessels to effect this purpose. Among those animals
which rank still higher in the scale of nature, you have
been told that another class of vessels — the absorbents —
become necessary to assist in the process of nutrition.
The simplest animals secrete without glands and respire
without respiratory organs, perform locomotion without
muscles, and exercise a will without visible nerves or
brain ; but those of more elevated character require the
aid of complete systems of distinct organs for each of
these vital operations. You must have observed, more-
over, that all the organs in these several systems, whatever
their special function may be, demand the presence of
capillary blood-vessels to carry nourishment into them
and absorbents to bear away their worn-out particles.
Blood-vessels and absorbents, therefore, form a part of
every organ in the body. This is easily proved by fill-
ing the arteries of an animal with a coloured injection,
which will be found to enter freely every organ except
the tendons, ligaments, articular cartilages, and the
cuticle with its appendages, (such as hair, horn, nails,
the enamel of the teeth, shells, &c.) Even in all these,
except the two last, the existence of vessels too minute
to receive injections may be inferred with much fairness
from the history of their diseases. The structure of the
articular cartilages is not yet clearly understood, and
the cuticle with its appendages is merely an inanimate
crust upon the surface of the body.

298. Not only the nutrition, but the special functions
of every organ, other than those just excepted (297), are
dependent upon the presence of the blood-vessels. In
the more complex animals and man, the stomach cannot
digest, the lungs cannot respire, the glands cannot

148 THE NERVOUS SYSTEM.

secrete, the skin cannot perspire, without the aid of the
capillaries furnished to them for the purpose ; and some-
times these capillaries are distinct from those that
convey nourishment to the same parts ; as is the case in
the lungs (259).

299. Now every organ, with the same exception (297),
is believed to be supplied with its appropriate nerves
from some nervous centre, which enter into its structure
and form a part of it ; and these nerves are just as
necessary, both to its nutrition and to its function, as
are the blood-vessels themselves. If we cut one cord,
the heart soon ceases to act ; if another, the stomach
loses its power of digestion, and the lungs fail to sepa-
rate the carbon from the blood, &c. ; so that every stage
of nutrition, in the more complex animals — the circula-
tion, absorption, secretion, and respiration — are under the
control of the nervous influence ; and you have been
informed already that feeling and muscular motion are
destroyed by the division of the fibres on which they
depend. The same is true with regard to the senses of
sight, hearing, taste, and smell, each of which may be
lost for ever by an injury to the nerve that supplies the
organ whose function it is to convey the impressions
made upon those senses.

300. Now the whole nervous system may be divided
for convenience into several portions, according to the
classes of the functions over which each group of nerves,
or nervous centres, is found to preside : and the term
system, in a more restricted sense, has been applied to
the two primary divisions of this great system. Thus,
when we speak of those nerves and nervous centres that
preside over the circulatory, digestive, secretory, and
other apparatus of organic life, w^e term them collec-
tively the nervous system of organic life: and when we
speak of those nerves and nervous centres that control
the five senses and the locomotive apparatus, we term
them the nervous system of animal life. It is needless
to explain what is meant by the names applied to the
lesser groups of nerves, such as the respiratory nerves,

NERVES OF ORGANIC AND ANIMAL LIFE. 149

the nerves of feeling, the motor nerves, &c., for these
names are indicative of the functions performed by the
organs which they designate.

301. The nerves of organic life are very irregular in
their course. Nearly all the ganglia in the body belong
to this class of nerves, and they are all bound together
into one system by branches passing from one ganglion
to another. They are placed, for the most part, in the
great cavities of the body that contain the lungs, heart,
great blood-vessels, the stomach, intestines, Hver, &c. ;
that is, they are located among the great organs of ani-
mal life, whose functions are governed by them. Their
minute branches travel with the blood-vessels all over
the body, to regulate the circulation, nutrition, and the
secretions of the secretory glands.

302. It is a curious fact, that all the organs governed
by this system are, like the nerves themselves, irregular,
and never arranged in exact pairs on opposite sides of
the body, like the organs of animal hfe. The blood-
vessels in the extremities of the larger animals do indeed
appear to be arranged in corresponding couples on oppo-
site sides of the body, but this appearance results en-
tirely from the necessity of the case. A man has two
arms, each containing similar organs to be nourished,
and each arm is provided with its proper great artery,
but if we trace these arteries to their origin from the
aorta, we find them altogether unlike in their commence-
ment. The artery of the left arm arises directly from
the aorta, while that of the right arm springs from a
great branch of the aorta, at some distance from this
latter vessel. In like manner, if we compare the minute
arteries, the capillaries, or the small veins of the two
arms, they will be found to present, in a remarkable
degree, that irregularity which is attached to every thing
connected with organic life.

308. On the contrary, the nerves of animal hfe are
remarkably regular, being disposed in corresponding
pairs, that take their rise in the brain or spinal marrow,
and are distributed to the correspondent organs on each
side of the body ; for all the organs of animal life, in-

150 THE NERVOUS SYSTEM.

eluding the osseous and muscular systems and the or-
gans of sense, are ranged in equal and very similar
pairs on opposite sides of the bod}^ like the arms and
the legs. Even the brain and spinal marrow, which are
portions of the nervous system of animal Hfe, are com-
posed of two opposite portions very similar to each
other, but united together in the middle so as to resem-
ble single organs.

304. You must not infer, from what has been stated,
that these two nervous systems are unconnected with
each other. Along each side of the spine, — that bony
column of the back found in all animals possessed of an
internal skeleton, — and on the front or anterior face
of this column, we find a row of ganglia nearly as
numerous as the separate 'bones into which the spine
is divided. These ganglia are connected together by
nervous cords throughout their entire series, and some
filaments from the upper members of the series even
enter the cavity of the head that contains the brain.
The whole range of the nervous centres just mentioned,
tosjether wdth all their connectino: cords, is called the
great sympathetic, or intercostal nerve, though, in fact,
it is rather a system than a single nerve. It gives origin
to the principal nervous filaments that are distributed to
the intestines; and also contributes to the formation of
the nerves that supply the lungs, heart, and stomach. In
addition to its direct connexion with the brain by means
of the filaments that enter the cavity of the head, it has
numerous connexions by means of branches with the
nerves of motion and feeling as they come off from tlie
spinal marrow (202). Thus this great nerv^e unites the
.system of organic life with that of animal life, and binds
into one entire system all the nerves of the body.

305. But you have been told that the functions of or-
ganic life are carried on without the consciousness of the
animal (136, 137) ; and this could not be the case if the
perceptive nerves of the organic system were capable
of the sense of feeling, or if the motor nerves of the
same system were subject to the control of the will.
For this reason, the impressions made on such nerves, in

SYMPATHETIC IRRITATIONS. 151

all animals that have an internal skeleton, are very im-
perfectly felt by the brain, in which is seated the con-
sciousness and the will of these animals. Still, as there
are numerous connexions between the ganglia of the
sympathetic nerves and the apparatus of feeling or touch,
that of voluntary motion, and the brain (304), you can
very well understand how, during health, the vague sen-
sation of hunger may be communicated to the brain, so
as to stimulate us to procure food as it becomes neces-
sary, and how a uniform feeling of comfort and con-
tentment should be spread over mind and body by the
just and proper gratification of all the purely physical
wants of our nature.

306. In diseases of the system of organic life, it is
necessary that the powers of locomotion should be pre-
vented from acting with energy, or the bodily disturb-
ance resulting from the exercise of the organs of ani-
mal life would be likely to render the disease w'orse,
or to check the efforts that the organs always make for
the purpose of correcting the disorder under which
they labour. Very wisely, then, is it ordered that the
connexion betw^een the two nervous systems should
enable the organs of animal life to perceive the danger
in which those of organic life are placed by disease.
Hence the strong desire of rest, the intolerance of light,
the weakness of the voluntary muscles, the feebleness
of mind, and even the great soreness of the ston:iach,
observed in many fevers which originate in the. stomach
or intestines.

307. In certain accidents we see still stronger jjroofs
of the mutual influence of the several parts of the ner-
vous system upon each other. I will give you a few
examples. A violent irritation of the intestines not un-
frequently occasions severe cramps of the muscles, and
particularly those of the lower extremi-ies, attended
with terrible pain, not in the intestines where the disease
commences, but in the limbs themselves. The Asiatic
cholera gives you an instance of this kind. Certain poi-
sons are well known to act upon the stomach in such a
manner as to produce horrible convulsions, accompanied

152 THE NERVOUS SYSTEM.

by a total loss of consciousness. Mere distention, by
over-eating, will sometimes arrest the functions of the
brain, as far as mf^ntal operations are concerned, without
disturbing the nerves of voluntary motion. Any very
severe and extensive injury to an organ indispensable to
the business of nutrition, will produce a great degree of
weakness of the whole nervous system ; so that the power
of the senses, the mind, the heart's action, the beating
of the pulse, the digestion, &c., are all most seriously
diminished ; and the animal, in great danger, deprived
of vital energy, sinks into collapse, as it is termed. After
a time the vital powers begin to recover their force by
resting. The heart commences acting with more vigour,
and continues to increase its exertions until they very
far exceed the proper standard of health. One organ
after another is wakened to more powerful efforts in
order to assist in repairing the injury, and the animal is
found to labour under a fever, which, unless managed
and regulated by art, may exhaust some weakened organ,
and thus ultimately destroy liff^ in attempting to restore
health. The practice of medicine consists, almost ex-
clusively, in the necessary regulation of these natural
consequences of injuries and disease.

308. Now, nearly all the connexions between the
nervous systems of organic and animal life are made
through the sympathetic nerves and their branches; and
of course their connexions are the cause of the asso-
ciated actions of parts so widely separated as the in-
testines and the extremities, the stomach and the brain,
&c., noticed in the four last paragraphs. These asso-
ciated actions are due to a cause of the nature of which
we know nothing more than we know of the nature of
attraction or gravitation. All we know is, that it acts
through the nerves and ceases when they are divided.
But it is convenient to give some name to this power,
and it has been termed sympathy, by the common con-
sent of physiologists.

309. When an impression is made upon one of the
ganglionic nerves by any thing occurring in the appa-
ratus of organic life, this impression is immediately con-

DEPENDENCE OF NERVES ON CIRCULATION. 153

veyed to the ganglion from which the nerve originates,
and the ganglion instantly transmits all necessary ner-
vous influences to the organs under its control. If the
importance of the impression demands the aid of other
organs, it is conveyed through the branches that con-
nect the different ganglia, so as to rouse them also
into action, and then the whole apparatus of organic
life may be called into exertion. If still further aid be
demanded, the message is forwarded to the brain and
spinal marrow, through the sympathetic nerves (304),
and we may then even feel pain communicated from the
heart, the stomach, the lungs, &c., but the sensation is
always vague and its location indistinct.

310. The cases in which the will has been known to
cause some slight disturbance of the functions of organic
life are rare, though no point in physiology is better un-
derstood than that occupation of the mind retards diges-
tion in the same manner with occupation of the muscu-
lar system (276), and all of you m.ust have observed
how greatly the vital operations are influenced by the
play of the passions, which, when very violent, not only
injure the health, but may even occasion sudden death —
a result that has been known to happen as well from
joy as grief In these cases it is not the brain alone
that suffers functional injury, for this would only destroy
the reason ; but even the heart and stomach are para-
lysed by their sympathy with the brain ; and without
the constant action of these organs, life cannot be
preserved in any of the more perfect animals.

311. You have now been made acquainted with the
close dependence of nutrition upon the circulation, and
the necessity of nervous influence to regulate the circu-
lation. You w^ill be little surprised to learn, then, that
the functions of the nerves themselves, like those of all
other organs, depend upon the supply of blood furnished
to them by their capillaries. This dependence is strictly
mutual ; for, if we prevent the blood from flowing to-
wards any particular nerve, it loses its power of receiv-
ing or conveying impressions, and the parts to which its
filaments are distributed become numb and cold by the

13^

154 THE NERVOUS SYSTEM.

destruction of their functions. On the other hand, if we
could remove all the sources of nervous influence from
any particular vessel or set of vessels, they would lose
their power of carrying on the process of nutrition in
the parts to w^hich they supply capillaries, and the same
numbness and coldness would occur in those parts, by
the arrest of their proper nourishment.

312. Thus you see that all parts of the frame are
linked together by bonds that cannot be broken with
impunity. Even man, with all his wonderful complexity
of organization, his thousands and tens of thousands of
vessels, his multitudinous machinery belonging to so
many different systems, his acute senses, his high feel-
ings and far-stretching powers of thought, which require,
in this state of existence, the aid of the most delicate
organs, constitutes but one complete machine, of which
no link, no cord can be disturbed without results that
are felt in every fibre. In whatever portions of the
frame the faint beginnings of disease may be perceived,
the actions that may result from it are capable of being
extended throughout the body ; and so nicely balanced
is this mysterious being as it comes from the hand of
the Creator, that

" When obedient nature knows his will,
A fly, a grapestone, or a hair may kill I"

Is it not, then, wise in us to seek diligently for the Httle
knowledge of this our fragile tenement which Provi-
dence has placed within reach of our understanding — a
tenement Hable to perpetual accidents, and alike threat-
ened with injury or destruction from an imprudent in-
dulgence of our physical desires or an unguarded burst
of mental feeling ?

313. In most of the foregoing remarks upon the ner-
vous system, I have referred chiefly to the condition of
the nerves as observed in those animals that have an
internal skeleton. Among the inferior orders that are
provided with external sheletons, the nervous system
appears to be entirely ganglionic, or, in other words, all
the nervous centres are ganglia, and there is no organ

NERVES OF THE INFERIOR ANIMALS. 155

that can be very fairly called a brain. It is true that in
many, if not most of these creatures, we find several
connected ganglia situated about the head, if there be a
head, or about the mouth, if there be not ; and where there
are any traces of special nerves of sight, hearing, taste,
or smell in these animals, they are found to originate
from these upper ganglia. You will frequently meet
with the term brain in works upon insects, worms, &c.,
written by naturalists of distinction. Whenever this is
the case, it is well to remember that these writers gene-
rally refer to the largest of the superior ganglia just
mentioned ; but we can discover no similarity of organi-
zation between this organ and the true brain of the most
perfect animals.

314. When we descend still lower in the scale of
nature, even the nervous centres disappear, a few scat-
tered filaments alone remaining; so that there is no
nervous system properly so called. At length no fila-
ments can be discovered ; and though nervous matter
is supposed by some writers to exist, even in these last
links of animated nature, in the form of detached grains,
this is a mere guess, and unworthy of serious attention,
at least in the present state of science.

315. The arrangement of the nervous system in its
simplest forms, among the lowest orders of animals,
somewhat resembles that of the nerves of organic hfe
in man ; and, as the whole history of animated nature
proves that the organic functions are brought to high
perfection much earlier in the scale of developement
than those of animal life, it may be fairly inferred that
these primary forms are really devoted mainly to the
regulation of the organic functions, when these functions
begin to require specific organs, which is not the case
in the hydra and the polypi. Yet all these animals,
however simple, give evidence at some period of their
existence, that they possess senses, instincts, and volition.
These functions, then, which in man and the other higher
classes of animals, appear to belong to the nervous sys-
tem of animal life exclusively, would seem to be exer-
cised by that of organic life in insects, worms, &c. ; nor

156 THE NERVOUS SYSTEM.

can we safely deny that they may reside in the mere
cellular tissue of the hydra, in which we can discover
neither a nervous filament nor a special organ of any
kind.

316. From what has just been stated, it is evident that
we cannot compare the nervous system of the inferior
animals with those of man and the other noble creatures
that possess a bony skeleton and a proper brain, with
any hope of improving our knowledge of the connexion
between the construction of the organs of sense and the
brain in the latter, and the functions that these organs
perform. If the bee displays an accuracy in the con-
struction of its honey cells, and a beauty of discipline in
the government of its little community of industrious
labourers almost equal to what is accomplished by man
himself with the aid of mathematical science and poli-
tical philosophy, and if all this be accomplished with
the assistance of a slender collection of ganglia and
ganglionic nerves, it does not follow that the brain is not
the instrument of all the instincts, feeling, and intellect in
the lord of the creation, and the centre of all the per-
ceptions that follow the impressions made upon the
organs of the five senses. Though this diflerence of
organization has been much insisted on by many who
oppose the modern doctrines of physiology on the sub-
ject of the functions of the brain, it is capable of a
ready and satisfactory ansv er. If, as you have seen,
a polypus can respire by means of its skin alone, while a
fish requires gills, and a quadruped lungs, for effecting
their more perfect respiration, it surely cannot be very
wonderful that an insect should display its instinctive
powers, wonderful as they may be, in consequence of
the structure of its principal ganglia, though quad-
rupeds and man require, for the exercise of their
far loftier mental endowments, the complex and sin-
gularly delicate organ, or system of organs, properly
called the brain.

317. The gradual separation of the vital functions —
w^hich seem to be all associated at first into one general
process of imbibition and transpiration accompanied by

THE CHAIN OR SCALE OF NATURE. 157

an obscure sense of touch and some traces of will — and
the formation of one set of specific apparatus after an-
other, observed as we advance from the hydra up to
man, has given rise to the general employment of a
term that I have been compelled to use more frequently
than I desired. I allude to the scale or chain of iLature.
You might be inclined to suppose, from the obvious tenor
of this term, that there was a uniform series of gradual
developement observable in all the details of organized
beings from the beginning to the end of animated nature.
Now, although we certainly perceive a regular gradation
in the perfection and energy of the vital functions, when
we cast our eye over the whole field of the animal
creation, yet we cannot discover the same regularity in
the structure of the several organs or systems of organs
as we pass from one great class of beings to another.
Thus, some insects may be much more complex, or, as
we might say, perfect in organization, than some worms,
while certain worms may be much more perfect than
most insects. The circulatory apparatus of many worms
is far more complete than that of insects, while the in-
stincts of many insects vastly surpass those that have
been heretofore observed in any worms. The same
remarks will apply, though with somewhat less force,
to comparisons between birds and quadrupeds, between
reptiles and fishes, &c. Providence appears to have
formed the animal kingdom upon several different mo-
dels that cannot be fairly compared with each other:
but this is a subject which belongs to that branch of
natural history which is termed zoology, rather than
to physiology. I notice it here, partly because I may
one day offer you a text-book upon zoology, to which
this volume may serve as a suitable introduction ; and
partly to prevent you from wasting time in after years,
over the worse than useless reveries of certain wild
theorists in physiology who have never felt the force of
two memorable lines of Pope the poet ;

" Why has not man a microscopic eye ?
For this plain reason, man is not a fly."

158 THE SURFACES OF THE BODY.

318. I trust you are now prepared to enter upon the
study of the organization of your own frames, so far as
it falls within the purpose of the present volume. I trust
that the broad view you have taken of animated nature
in general will prove useful in several ways : First ; by
proving the universality of the physiological laws that
should regulate the health, habits, and morals of man :
Secondly ; by making you familiar with the true mean-
ing of the few technical terms that are necessarily used
in the current of our studies : and lastly, by enabling
you to comprehend more fully the treatises and essays
on anatomical and physiological subjects which you
may meet with in the course of your future reading.

CHAPTER IX.

OF THE SURFACES OF THE BODY.

319. When you look at the entire body of a human
being, you perceive that it is naturally divided into
several portions or regions, associated into one complete
frame. Of these divisions, the most striking in impor-
tance are the head, the neck, the trunk, the superior ex-
tremities, and the inferior extremities.

320. Most of these grand regions are again subdivided
into lesser regions, which it is well to name, in order
that you may understand the meaning given to some
very familiar words used by writers on anatomy and
physiology in a sense somewhat diflerent from that in
which they are received in ordinary conversation.

321. If you draw a cord or string across the root of
the nose, and carry the two ends toward the outer
angles of the eyes, round the sides of the head across
the openings of the ears, and bring them together at the
nape of the neck, it may be considered as dividing the
head into two portions. The portion which lies above the

GRAND DIVISIONS OF THE BODY. 159

string contains the brain, and those portions of the bones
of the skull called the cranium, which enclose that all-
important part of the nervous system, together with
certain muscles or parts of muscles, and the integuments
or skin of the head, with its appendages. This portion
constitutes the head proper, as distinguished from the
face.

322. All that portion which lies below the string is
called face by anatomists, and you observe that it does
not include the forehead, as, in familiar language, the
term usually does.

323. The word neck is employed by anatomists in its
popular sense.

324. The trunk is divided into two great portions,
called the chest or thorax, and the abdomen. If you
pass your hands all around the body, from the lower
end of the breast-bone along the inferior margin of
the ribs and directly across the back from the poste-
rior end of tlie lowest rib on one side to the correspond-
ing point on the other side, you encircle the trunk with
a line which separates these two great portions. All
the surface that lies above the line belongs to the thorax
or chest ; all below the line appertains properly to the
abdomen.

325. But it has become customary to consider the
lower part of the abdomen as a third great division of
the trunk, and to give it another name. If you carry
your hands down the sides of the body, from the mar-
gin of the ribs along what are usually called the
flanks, you soon perceive that the lower part of the
trunk is enclosed, beneath the skin and other superficial
parts, by solid bones. The names and general form of
these bones you will learn hereafter, but their extent and
outHne are sufficiently plain. That part of the trunk
which is included within these bones is called the pelvis.

326. The chest contains the lungs or breathing appa-
ratus, the heart, some of the great blood-vessels, the
canal that conveys the chyle to the blood, and certain
other organs accessary to these parts.

327. The abdomen and pelvis are chiefly appro-

160 DIVISlOPfS OF THE EXTREMITIES.

priated to the accommodation of the alimentary canal,
from the stomach downwards, and the numerous large
glands or other organs which contribute to the process
of digestion; such as the hver, the pancreas, the spleen,
&c. &c.

328. The joints by which the superior extremities are
connected with the trunk are called ihe shoulder joints ;
and the upper end of the bone of the arm, the shoulder-
blade, and collar-bone, — which well-known parts con-
tribute to form these joints, — taken together with the
muscles or flesh, the skin, &c. covering these bones,
are called the shoulders.

329. The arm^ as known to anatomists, is that pari
of a superior extremity that intervenes between the
shoulder-joint and the joint of the elbow. The portion
embraced between the latter and the wrist-joints is
termed \k\Q fore- arm.

330. The other divisions of the wrist and hands will
be better understood when we consider the structure of
the skeleton. The same thing ma}^ be said of the foot ;
and it is unnecessary to specify the remaining portions
of the lower extremities, because the terms in common
use are applied to these parts without any modification
of their meaning.

331. The body, viewed as a whole, may be regarded
by the physiologist as a great mass of cellular tissue
analogous to that which forms the hydra and the polypi,
constituted, in some places, of very large and complete
membranous cells ; in others, of smaller compartments
communicating freely with each other, and, in many
situations, strengthened with numerous fibres, so as to
form a strong network, or those broad and firm expan-
sions known by the name of fascise.

332. But the extensive sphere of action designed to
be filled by an animal so important in the scale of
creation as is man, demands that he should be furnished
with almost innumerable special organs for the perform-
ance of particular functions ; and to this end the vital
powers of many different portions of the cellular tissue
are so modified, that in one place the cells become filled

LAYERS OF THE INTEGUMENTS. 161

with secreted flesh or muscular matter ; in another, with
the peculiar substance composing the nervous fibre, &c.

333. In the earlier part of this little volume you were
told that even the hydra had an external covering form-
ed of more dense materials than the soft cellular tissue
of which the mass of its body and arms are composed,
and this external covering was called the skin of the
animal.

334. You were informed, also, that this covering pre-
sented the same appearance, and performed the same
functions, both on the outside of the body and within
the cavity for the reception of its food (61).

335. Now, man, owing to the complexity of his struc-
ture, requires a covering much less simple than that of
a mere polypus or hydra. Accordingly we find his skin
composed of several layers, differing widely from each
other.

336. The first, or outer layer of the skin, is called the
epidermis, cuticle, or scarf-shin. It is an organized mem-
brane, because it resembles nothing that is found among
inorganic bodies ; but it does not appear to be endowed
with life, for it performs no active function. You see
the cuticle raised from the surface when blistering oint-
ments are applied, or when a person has been scalded.
It possesses no power of feeling, and you may readily
pare it off from the palm of the hand with a penknife.
After bathing, considerable portions of it are rolled into
little scrolls, and carried away by the towel.

337. When you examine a piece of cuticle detached
by a knife or scissors, you find it to resemble a very
thin transparent piece of soft horn. In many parts of
the body it is extremely thin and delicate ; but in parts
designed to bear a great deal of pressure and rough
usage, it becomes solid and thick ; as in the palm of the
hand, on the heel, the ball of the great toe, &c.

338. You have been already told that the clav^^s, horns,
and shelly coverings of animals, are productions or ap-
pendages of the cuticle (156). Even man is not with-
out some such means of protection or defence ; and in
the nails you see the horny character of cuticle almost

1G2 LAYERS OF THE INTEGUMEXTS.

as plainly displayed as it is in the tortoise-shell of which
combs are made.

339. The cuticle is a secretion poured out upon the
surface of the body by the Hving parts immediately be-
neath it. At first it is soft or almost fluid ; as you per-
ceive if you examine it when beginning to appear on
the surface of a blister after the old cuticle has been
cut away; but it is not dissolved by water or by perspi-
ration ; and it very soon hardens, like a varnish in dry-
ing, over every part of the body.

340. You often hear of the pores of the sldn, and
perhaps you may think that you actually see them scat-
tered over the back of the hand ; but this is a deception.
There are no regular orifices to be found in the cuticle ;
but it is spongy, and thus permits the perspiration to
flow through it every where with facility. The uneven-
ness of the cuticle is entirely owing to the irregularities
of the other layers of the skin, over which this varnish
is spread.

341. There are, indeed, two sets of depressions in the
cuticle that resemble holes, though they are not so in
reality. The first set is seen very conspicuously about
the nose, where they are unusually large. They corre-
spond with as many peculiar sacks, buried or formed in
the deeper layer of the skin, and known by the title of
sebaceous follicles.

342. In order to preserve the skin in a soft and pliable
condition, it is necessary that it should be freely supplied
with an oily or cheesy matter, and it is the office of the
sebaceous follicles to secrete this matter. When it be-
comes unusually abundant, or unduly hard, it may be
pressed out of these little cavities by pinching the part
with the thumb and finger, and it is then often mistaken,
by the vulgar, for " little worms." When cleanliness is
neglected, the contents of the sebaceous follicles collect
the particles of dust floating in the air, and produce the
appearance of small, black specks upon the face, not
always easily removed.

343. But, although these cavities are peculiar secreting
organs, somewhat resembling glands (224), the cuticle

LAYERS OF THE INTEGUMENTS. 163

is not interrupted in its passage over them, but dips into,
and lines the sacs ; being rendered very thin and less
solid in such situations.

344. The second set of seeming orifices in the cuticle
correspond with the hairs that are scattered over the
body.

345. The hairs take their root in the inner layer of
the skin, far below the general level of the cuticle, and
each particular hair grows by a secretion taking place
at its lower end, where a special organ, of very curious
structure, is provided for this purpose, each one being
furnished with its proper capillary blood-vessels, and its
own proper branch of a nerve. But the hair itself resem-
bles a tube of horn or cuticle, and the manner in which
it is formed does not differ materially from that which
produces the epidermis, the nails, and other similar parts.

346. As a young hair begins to grow it gradually
makes for itself a passage through the thickness of the
inner layers of the skin, and at length appears above
the surface. But the cuticle dips into this canal from
the moment of its completion, and lining it for some dis-
tance, as in the case of the mucous follicle, unites with
the hair so intimately that no orifice is allowed to exist
there.

347. The cavity of the horny tube of the hair is filled
with a peculiar substance, secreted by the blood-vessels
about its root or bulb, and this secretion shining through
the transparent walls, gives the hair the great variety of
colour observed in different races and individuals. When
age or disease diminishes the vital power of the vessels
of the bulb, the internal secretion is often arrested, while
the horny matter continues to grow as before. The
hair then becomes gray, or silvery white. If the vital
power of the bulb be still farther diminished, the horny
matter is no longer formed, the hair falls out, the cora^
mon cuticle grows over the canal, which is soon oblite-
rated, and the part becomes permanently bald.

348. The functions of the cuticle are entirely passive,
or mechanical. It protects the delicate and exquisitely
sensitive extremities of the nerves of touch from being

164 LAYERS OF THE INTEGUMENTS.

injured by the immediate contact of external bodies. It
prevents "the fluids of the soft parts beneath from being
carried oft' by evaporation too rapidly; and it also pre-
vents the blood in the superficial vessels from being
brought so near to the atmospheric air as to be changed
in character by spontaneous respiration, which would
cause it to prove altogeiher too stimulating for the pur-
poses of life in such situations. If man could endure
the danger, the pain, and the exhaustion of living with-
out a cuticle, he would have no occasion for lungs, and
might defy consumption. Fig. 39, a.

Fig, 39.

Section of the Skin.

a. The cuticle, b. The rete mucosum. c. The papillary portion of true skin.
d. The fibrous portion of true skin. e. Cellular tissue beneath the skin. /. Some
fibres of the fleshy panicle.

349. The cuticle being removed, we next observe the
living membrane beneath, which secretes it. This is
exceedingly tender; being composed of very delicate
cellular tissue, with innumerable capillary blood-vessels
winding within it. There is an equally incalculable
multitude of the naked and expanded extremities of the
nerves of touch or tact passing up from beneath it, so
as to render its surface irregular, and produce the cor-
responding roughnesses observed upon the cuticle.

350. These nervous expansions and their accompany-
ing blood-vessels, which properly belong to a third layer
of the integuments, to be presently noticed, are called
papillcc, and all the nerves of the senses of feeling and
taste appear to terminate in this manner. The mem-
brane, or layer of cellular tissue, covering and loosely

LAYERS OF THE INTEGUMENTS. 165

connecting these papillas, is called the rete mucosum, or
nnucous network. It is the middle layer of the skin,
and in it is deposited that peculiar colouring matter
which gives to each natural or accidental race of men —
the red, the white, the olive, and the black — and to each
individual, whether brunette or blonde, his own especial
hue. Fig. 39, b.

351. This colouring matter is probably designed to
protect the tender parts beneath from the too powerful
action of light, which penetrates the cuticle with great
facility. It is found in greater quantity, of a darker hue,
and deposited in a thicker membrane, in the animals and
men inhabiting the warmer parts of the world ; and it
is scarcely discoverable in many of those residing near
the polar regions. Habitual exposure very gradually
deepens the colour on the exposed parts, and there is
every reason to believe that the peculiarity thus pro-
duced has, like most other individual characteristics, a
tendency to become hereditary. Those Hindoos who
belong to castes condemned from time immemorial to
labour in the burning sunshine and in the open air, are
generally found nearly as black as many negroes, while
those who have been devoted, for many generations, to
tiie occupations of priesthood and the pursuits of litera-
ture, are often paler than the palest American Indians.
But these questions of the influence of climate on colour
must be regarded as somewhat speculative. The extent
of such influence can never be fully ascertained; as
ages would be required for the necessary observations,
and the effects of other causes of similar changes can-
not be fairly estimated.

352. The colouring matter of the hair and the eye
is probably of the same nature with that of the skin;
and it is observed that the inhabitants of the higher
latitudes are almost universally remarkable for their
light hair and light blue eyes. The quadrupeds and
even the fishes of the polar circle give evidence of the
truth of this general rule. The common bear and the
ermine of those regions are entirely white. A species
of the dolphin of the sfime colourless character is also

14*

166 LAYERS OF THE INTEGUMENTS.

seen in the antarctic regions; and the birds of those re-
gions have generally a white or very light blue plumage,
with a skin of a corresponding pale colour. Even in
milder climates, one of the hares and a ferret are found
to be covered with black fur in the summer and white
in the winter.

353. The third and inner coat of the skin is called
cutis vera or true skin. Fig, 39. c, d. By many anato-
mists it is supposed to be composed of two distinct lay-
ers, the outer of which they term the papillary body
(350), seen in the figure at c. But this multiplication of
membranes almost artificially, though sometimes useful
to the profound physiologist, tends only to confuse the
learner. I shall therefore consider the true skin and the
papillary body as a single layer.

354. The true skin is composed chiefly of dense cel-
lular membrane, strengthened by very strong fibres, and
penetrated by innumerable capillary blood-vessels and
nerves. The network of fibrous matter forming the
principal part of this membrane leaves very numerous
irregularly conical openings between the meshes ; through
which the extremities of the fibres of the nerves of feel-
ing, each with its accompanying capillary arteries and
veins, pass out to the external surface of the membrane,
in order to form the papillary body. These conical cavi-
ties are comparatively wide on the inner side of the skin,
but become very narrow before they reach the outer
surface. They are filled with loose and very delicate
cellular membrane, binding together the capillary blood-
vessels and nerves while allowing the former sufficient
freedom of action.

355. On the outer surface of the true skin, immedi-
ately beneath the mucous layer, the nervous fibres ter-
minate in an expansion of soft and pulpy nervous
matter, supposed by many to consist of cineritious
matter (283) and surrounded by an inconceivably deli-
cate network of capillaries. The little eminences thus
formed are the papillas of the skin (.^^50), and in them
resides the sense of touch in the highest degree of
refinement. When inflammation attacks the true skin,

LAYERS OF THE INTEGUMENTS. 167

the papillge are often subjected to extreme pain, from
the swelling of the contents of the little fibrous cones
while the fibres cannot enlarge themselves sufficiently
to accommodate their increased bulk. The commence-
ment of the mortification that attends upon a carbuncle
is occasioned by the swelling becoming so great that
the pressure of the fibres closes the capillary vessels as
they pass through the true skin, and thus destroys the
life of at least the outer portion of the membrane.

356. The root of every hair is seated upon a little
organ called the bulb, which is constructed somewhat
like a gland, being supplied with its proper blood-vessels
and nerve. This organ secretes the hair, by adding layer
after layer to the horny matter at its base, and perpe-
tually thrusting outward the older portions. The bulbs
of the hairs are seated in the innermost portion of the
true skin, and often project below the general level of
the membrane into the cellular tissue beneath, so that
many physiologists regard the hairs as originating
altogether w-ithin the skin. This position is evidently
incorrect ; for when the true skin is raised by an acci-
dent, the hair invariably comes with it, without any
injury to the bulbs. The latter are therefore included
in the true skin which forms little extensions or fro-
cesses inward from its surface, in order to include them.
. 357. All the essential active functions of the skin ap-
pear to be performed chiefly, if not entirely, by the outer
surface of the true skin. The vessels of this part supply
the materials for perspiration and those also of which the
cuticle is constructed. The nerves of the skin, as has been
stated, are the principal seat of the sense of touch. When
that sense is exercised, or when irritants of any kind
excite pain in the part, there is an instantaneous rush of
blood to the capillaries, and the papillae are enlarged
and rendered much more sensitive. From the influence
of cold, or certain affections of the nervous system that
produce the sensation of cold, the cellular tissue of the
true skin is made to contract. The papilke then become
very prominent, and give rise to the appearance called
goose-flesh ; but the blood-vessels being compressed by

168 LAYERS OF THE INTEGUMENTS.

the contracted tissue, the sensibility of the nerves is
diminished.

358. Many quadrupeds and other aninnals have an
additional layer or fourth coat of the skin, called the
J?e5/?7/;?rtW7zzc/e, consisting of light-coloured long muscu-
lar fibres, originating from one part of the cutis vera,
and inserted into another part. The principal function
of these fibres is to shake or agitate the skin so as to
drive away insects, and to rid the animal of other
annoyances. They are so powerful in the elephant, that
he is able, by their means, to throw an unskilful ridei
who ventures to seat himself on the back instead of the
neck.

359. These muscular fibres are often connected with
the bulbs of the hairs or feathers in certain parts of the
body ; and this will explain to you the power of dogs,
cats, hogs, the eagle, and many crested birds, to erect
their manes or feathers when angry. All birds appear
thus to elevate their feathers when bathing themselves.

360. In man, this muscular coat is seen only in a few
particular parts of the body ; as about the neck ; but
enough is preserved to show the beautiful simplicity of
plan displayed throughout the animate creation, and to
explain some points in relation to the interior structure
of the frame not otherwise so clearly intelligible ; as,
presently, we shall have occasion to perceive.

361. To prevent the confusion likely to result from
the generic term skin, as applied in popular language to
the assemblage of all the layers of v^diich we have been
speaking, while, by the physiologist, it is commonly con-
fined specifically to the cutis vera* (353), I shall substi-
tute the w^ord integiiments hereafter, when speaking of
the various coverings of the body already described.

* We meet with many tolerably well educated people, who seem
through life to have a very imperfect idea of the distinction between a
g-enus and a species, which ignorance is the more excusable because
their dictionaries will rarely be found to communicate a clear idea of
the subject. If the pupil will endeavour to acquire this knowledge from
his preceptor or parent, he will find it useful on many other occasions
than the present.

ARRANGEMENT OF THE INTERNAL INTEGUMENTS. 169

362. The various membranes, layers, or coats com-
posing the integuments, are not placed loosely over each
other, but, with the exception of the cuticle or epidermis,
they are bound so firmly together by the common cel-
lular tissue, — which, as you have been told, penetrates
and constructs all parts of the body (165), — that they
appear like a single cloak or envelope, varying from one-
sixteenth to three-sixteenths of an inch or more in thick-
ness, and covering all the outside of the person. When
you divide them, you find it much more easy to raise
them bodily or strip them off from the parts beneath,
than to dissect the difl^erent coats of which they are
composed, one from another.

363. The integuments of the surface of the body are
connected with the fascise or muscles over which they
are placed by more or less of the common cellular mem-
brane, which is very loose in most places, permitting them
to slide freely and to a considerable extent. But on the
soles of the feet, in the palms of the hands, along the
middle line of the back, and some other places, the
tissue is strengthened by numerous fibres, and the skin
is very firmly bound down to the parts within it.

364. In persons improperly called fleshy, the fat to
which they owe their bulk is principally deposited in
this sub-cutaneous cellular tissue, but it cannot accumu-
late in great quantities where the skin adheres in the
manner described in the last paragraph. Could it do so,
the hands and feet might become entirely useless by
their bulk.

365. All the internal passages of the body communi-
cating with the surface, even to the last branch of the
ducts that convey the several secretions to their desti-
nation, are lined or formed by the integuments. And
to give you a clearer idea of this fact, I will describe
the arrangement of these membranes after they enter
the mouth and nose to form the alimentary canal.

366. At the mouth and nose, the external integuments
are reverted inwards, so as to cover every part of the
walls of these cavities : but the blood-vessels of the true

170 ARRANGEMENT OF THE INTERNAL INTEGUMENTS.

skin forming these walls become larger, while the cuti-
cle diminishes in thickness and increases in transparency
until the blood in the capillaries shines through, giving
to the lip its beautiful colour, and to the tongue and
throat a still deeper tint. This delicate cuticle now
takes the name of epiiheHum^ though there is no good
reason for this multiplication of terms.

3G7. The follicles of the skin, which are here more
numerous and often much larger than they are exter-
nally, secrete mucus instead of the sebaceous matter
poured out upon the common cuticle. The true skin is
considerably modified also ; but notwithstanding these
apparent changes, the internal integuments are merely
extensions of those already described externally.

368. Immediately behind the nose and mouth, the
integuments form a large sac, into which both these
passages open. It is called the jjharynx, and termi-
nates below in an irregular funnel continued into the
canal by which the food is conveyed to the stomach.
Outside of the mucous membrane corresponding with
the rete mucosum, we find a layer of firm and some-
what fibrous cellular tissue answering to the true skin:
and enveloping this, we observe the fleshy panicle (3.58)
very much developed, forming three strong muscles,
which overlap eacti other, and are capable of con-
tracting so as to diminish the size of the pharynx, and
force its contents downwards into the canal leading to
the stomach, called the oesophagus. The fibres of this
muscular coat are found running in several difi^erent
directions around the sides and back of the pharynx
until you descend to the commencement of the oesopha-
gus. They are then chiefly arranged in the circular
and longitudinal directions, so that they can compress
or shorten the canal as the motions of the food require
it to be altered in form. As soon as the oesophagus
(thus composed of the epitheliuin, the mucous mem-
brane, the cellular coat, and the muscular coat,) has
passed through the chest (324) and enters the abdomen,
it expands itself into a large, irregular bag, called the

STRUCTURE OF THE INTERNAL HVTEGUMENTS. 171

stomach ; from the lower end of which the alimentary
canal is continued in a manner to be described hereafter.

369. After the epithelium has lined the inner side of
the oesophagus and entered the stomach, it ceases sud-
denly at the upper end of that organ ; and the mucous
coat becomes the lining membrane throughout the re-
maining portion of the alimentary canal.

370. It is impossible to conceive of any thing more
delicate than the incalculably fine network of capillary
vessels that penetrate most portions of the mucous coat.
They are so fine, and approach so near the surface, that
when filled with glue mingled with vermilion, after
death, the surface appears uniformly red. I have even
seen the glue flowing through the sides of the vessels
and the men:ibrane into the canal, completely strained
and colourless; not a particle of the vermilion being
able to accompany it. This will explain the ease with
which the blood-vessels can pour out the secreted mucus
that lines the alimentary canal, and also, the facility with
which the lacteals originating on this surface can select
the chyme from the mass of food as it passes.

371. The manner in which the fibres of the nerves of
organic life terminate upon the mucous membrane is less
understood than that observed in the nerves of feeling
beneath the rete mucosum (355) ; but in those parts of the
alimentary canal in which absorption is carried on most
rapidly, the whole surface of the membrane is covered
with little hair-like appendages composed of capillary
veins, arteries, absorbents, and probably nerves. These
are called villi, because they give the surface the
appearance of velvet. They correspond with the pa-
pills of the skin.

372. Among the villi and on other parts of the mem-
brane we discover the orifices of innumerable small mu-
cous follicles, and these are collected together in large
groups in certain parts of the canal where, from their
peculiar structure, they hav^e been termed glands and
have received special names. But, though a knowledge
of the history of these organs is all important to the
physician, it is needless to describe them here.

■Hi

172 STRUCTURE OF THE INTERNAL INTEGUMENTS.

373. You now perceive that the integuments, though
possessing every where the same general character,
have a much more complex organization in some places
than in others. Yet we find throughout their whole extent,
"whether viewed internally or externally, the two princi-
pal layers — the dense cellular layer like the true skin, and
the mucous layer, like the rete mucosum. The other
two layers appear only occasionally, where they are
wanted, — the cuticle principally on the outer surface, as
a protection to the delicate papillas and for other pur-
poses, and the muscular coat chiefly around the ali-
mentary canal, to urge forward the food as the process
of digestion advances.

374. The integuments thus constructed penetrate into,
or rather they form, every little duct communicating
•with the internal surface of the body. Thus, the gall
duct is constructed by the integuments of the small
intestine just below the stomach. TJiey here extend
themseh^es into a long canal leading to the liver. On
the outside of this organ, the canal expands itself into a
sac, called the gall bladder, which receives and retains
the bile until it is wanted to promote digestion. At a
short distance below the neck of this sac, the duct
sends off a large branch which passes into the substance
of the liver, and divides there again and again until its
capillary branches reach every part of the organ, to
convey thence the peculiar secretion of this enormous
gland. Throughout its entire course, the gall duct is
constructed on the same general principle with other parts
of the integuments ; but it has a muscular coat only
where this is necessary for the purpose of promoting or
checking the flow of bile towards the intestine. Behind
the root of the tongue, and before the commencement
of the oesophagus, is placed the upper extremity of the
organ of the voice, called the larynx, Fig. 32, 1, page
123, which admits the air into the trachea. It opens into
the pharynx by a narrow orifice, of which I shall speak
more fully hereafter. Now, when the integuments of
the mouth and the pharynx reach this orifice, they enter

STRUCTURE OF ACCIDENTAL INTEGUMENTS. 173

It, (becoming somewhat modified in their organization,)
and line the inside of the trachea and bronchico even to
the air-cells of the lungs. From the cavity of the nose
the integuments extend themselves through a passage in
the bones of the face, and form a canal for conveying
the tears from the eye. This canal has also its sac or
expansion near the upper extremity. But it is needless
to quote more instances in illustration of the general
principle that all passages communicating with the sur-
face are formed by the integuments, and bear a close
resemblance to the skin.

375. Even when disease produces an opening com-
municating with the skin, if it be narrow and does not
heal for a long time, the vital powers at length cover it
with integuments which sooner or later present the
appearance of the mucous membrane, and the canal
becomes converted into a part of the surface. Such
passages are called fistuloe. They are sometimes pro-
duced artificially by the surgeon for the cure of more
formidable diseases. To give you a clearer idea of this,
I w^ill mention an operation by which a very disagree-
able consequence of certain wounds of the face has
been occasionally cured. The principal gland that
secretes the saliva poured into the mouth is placed over
and behind the lower jaw, near the ear. Its duct runs
forward towards the middle of the cheek, and there opens
into the mouth, where you can see the orifice projecting,
like a little pimple, opposite the grinding teeth. Now,
in wounds of the cheek, this duct is sometimes divided ;
and then the saliva cannot find its way into the mouth,
but flows out upon the cheek, keeping the wound from
healing. The part of the duct that has been cut off
then becomes closed, and an operation is rendered
necessary to restore the saliva to the mouth. For this
purpose a passage is made by the knife, from the
bottom of the wound directly through the cheek. A
leaden ball or button threaded with many strands of
silk is next procured, and the silk being passed through
the cut into the mouth, the button is drawn into the

174 STRUCTURE OF ACCIDENTAL INTEGUMENTS.

wound, close to the divided end of the duct. It is then
easy to cause the skin to heal over the lead, while the
saUva flows along the silk. After the healing, the
button is removed by cutting upon it from within the
mouth, and the constant flow of the secretion keeps
open the new canal. In a few weeks, this new passage
is found to be converted into a part of the duct, and is
provided with regular integuments.

376. But the most remarkable proof of the similarity
of structure observable in the internal and external
integuments is the ease with v\hich the mucous mem-
brane changes into skin when kept dry by evaporation
and exposed to light and air, and the equal readiness
with which the skin becomes converted into mucous
membrane when deprived of light and air and kept
in a moist condition. Instances of the former kind
you would not comprehend without more anatomical
knowledge than is intended to be conveyed in this
volume ; but cases of the latter class are sufficiently
familiar.

377. In young children and elderly people who are
remarkably fat, the skin of the neck is frequently thrown
into folds, so that a part is doubled inward until the light
and air cannot freely reach it, while it is kept constantly
moist by the condensation of the insensible perspira-
tion (209), which cannot escape in the form of vapour.
In such situations, the cuticle first swells, as it does on
the hands of a washerwoman, and at length falls off in
places, leaving the mucous surface of the skin exposed,
and the papillae in a great degree unprotected. The
slightest accidents are then productive of great pain.
If an attempt be made by the rete mucosum to secrete
a new cuticle, it takes the form of a mere epithelium,
and soon falls off again unless the part is occasionally
exposed to the air. The terribly painful sores some-
times occurring between the toes, even in careful per-
sons, are produced in precisely the same way. All such
cases are readily cured, if taken in time, by frequent
washing to remove the moisture of perspiration, and then
exposing the part freely to the air, or dusting it again and

STRUCTURE OF ACCIDENTAL IxXTEGUMENTS.

175

again with some mild dry powder. The new mucous
membrane is then reconverted into skin.

378. Even here in the history of man, you see the
simplicity of nature vindicated ; for these remarks must
have reminded you of the fact, that, in the hydra and
polypi, the inner and outer surfaces are mutually con-
vertible into each other.

379. You now perceive, most clearly, that the whole
frame of man, with all its delicate machinery, is com-
pletely enclosed in an unbroken cover of integuments,
through w^hich every thing that enters the body, as well
as every thing that leaves it, must necessarily pass. The
whole frame may be compared to a cylindrical tube,
and its surface, physiologically speaking, is not confined
to the outside of the person. On the contrary, it is many
times more extensive than the whole exterior. It in-
cludes the entire length of the alimentary canal, which,
as you will hereafter learn, is at least thirty-six feet in
length in a man measuring six feet in height. It includes
the whole extent of the air passages, the larynx, the
trachea, the bronchia, and the air cells of the lungs. It
embraces the cavities of the mouth and nose, with the
front of the eye and the tear-duct; and it even extends
into several cavities within the solid walls of the bones
of the upper jaw and several of those of the cranium,
as will be explained in the next chapter.

380. Throughout by far the greater part of this vast
surface, the delicate integuments are unprotected by a
cuticle ; yet they are every where liable to be acted
upon injuriously by external agents. When 3^ou con-
sider how severe is the pain produced by applying vine-
gar, brandy, or pepper to the surface of a blister after
removing the epidermis ; and when you reflect upon the
follies into which we ai^ continually led by the indul-
gence of appetite, you will fully comprehend the benefi-
cence of Providence in supplying all the internal inteo;u-
ments with nerves of organic life, incapable of causing
the sensation of pain, except when seriously diseased
(305). Around the orifices of the mouth and nose, the
sensibihty of the nerves is very acute, and the thin epi-

176 IRRITABILITY OF THE ORIFICES OF CANALS.

thelium allows them to be acted upon by the slightest
irritant, in order that we may be warned in time of the
presence of any thing injurious in our food or in the air
that we breathe ; but the moment any powerful stimulus
is fairly admitted into the alimentary canal, it ceases to
produce pain, unless it acts as a poison and warns the
mind of the danger through the medium of the sympa-
thetic nerve (306).

381. At the orifice of the larynx, the sensibility of the
integuments is so acute that even so mild an article as
a drop of water cannot touch it without giving rise to
a most violent cough and severe suffering ; yet if, as
sometimes happens, a pea or any other hard sub-
stance makes its way completely into the trachea, it is
no longer felt until it produces disease. I once saw a
young medical man in danger of destroying life from
ignorance of this fact. A woman attempted suicide
with laudanum. It was necessary to pump up the poi-
son by means of a tube passed into the stomach. The
surgeon passed the tube backwards to the throat, and
instantly there was a violent effort to cough, and appa-
rent suffocation. He did not pause, but hurried the tube
downward, and the cough and spasm immediately ceased.
He was on the point of forcing through the tube a quart
of water, when I arrested his hand. The tube was in
the lungs and not the stomach, but the instrument had
passed the irritable part of the orifice of the larynx, and
the patient breathed by the side of the tube. It was
withdrawn and introduced again into the oesophagus,
and the woman was saved.

382. When persons are drowned, or suffocated in cer-
tain poisonous gases, the water or foul air so acts upon
the orifice of the air passage, that it is closed by a vio-
lent spasm, and not a drop of the water or a particle of
the gas finds its way into the lungs until long after
death. Were it not for this provision of Providence,
such persons would never be recovered from the state of
suspended animation.

383. It has been stated in the earlier part of this
volume, that a considerable quantity of water escapes

ARTIFICIAL OBSTRUCTIONS OF PERSPIRATION. 177

from the lungs in the form of vapour during the act
of expiration. This compensates in part for any de-
ficiency in the power of the skin to purify the blood
of its surplus water and certain salts (for perspiration
always contains a portion of salts), by means of the
ordinary secretions of the integuments. It was also
stated that the skin of man was capable of contributing
to the process of respiration, as does the back of the
frog and the w^hole surface of many animals of less
perfect organization. Now if our habits should pre-
vent the free exercise of these functions of the skin,
the lungs would be compelled to exert themselves so
much the more industriously, in order to make up for the
deficiency. They must respire more laboriously, and
must discharge a larger portion of watery vapour with
the breath. Such causes unavoidably produce debility
from over exertion of the lungs in matters beyond the
proper limits of their functions, and assist in bringing on
consumption or other diseases of the chest. Care with
regard to frequent ablutions, and the removal of the su-
perabundant cuticle by means of the coarse towel or
flesh-brush, therefore, promote essentially the healthful-
ness of the lungs. It has been found, practically, that
the long continued and daily use of India-rubber cloth
garments, covering a large portion of the person, checks
in great degree the insensible perspiration and the respi-
ration of the skin, and produces fatal consequences in
the manner just described. The freedom with which
the air and moisture find their way through flannel
has, probably, much to do with its healthfulness as an
article of dress. But I am not now writing on Hygiene,
(the art of preserving health,) and these illustrations are
introduced merely to show you the practical utility of
facts and principles that may seem dull and uninterest-
ing when not thus forcibly impressed.
15*

178

CHAPTER X.

OF THE SKELETON AND ITS APPENDAGES.

384. The several different classes of organs connect-
ed with the osseous system — the bones, the articular car-
tilages, and the ligaments — have been specified, and
their general nature defined in a fi^rmer chapter, (chap-
ter V.) ; and it would be advisable for you to revise
what is there stated, in order more fully to comprehend
the following remarks.

385. The skeleton of an infant is, apparently, com-
posed of many more pieces than that of an adult, be-
cause when the earthy matter or carbonate of Hme
begins to be deposited in the gristle, of which the entire
bones are formed during the second stage of their growth
(159), this new secretion commences in several parts of
the same bone at about the same time. The intermediate
space continues to resemble cartilage until the earthy
materials of the difierent portions undergoing the pro-
cess of complete ossification (160) are so far increased
in quantity that this space is obhterated. Let us take
the bone of the arm as an example. The two extremi-
ties of this bone, w^hich contribute to the formation of
the elbow and shoulder joint, ossify separately from the
shaft ; from which they are widely detached for a consi-
derable time by gristle. It is not until the individual
approaches mature age that all the bones are rendered
perfect. This provision of nature is all-important to our
safety during childhood ; for it increases the flexibility of
the bones, and deadens the effect of the innumerable
falls and other accidents of early life.

386. But, even in the adult, the skeleton consists of
a multitude of pieces. Without counting the teeth, the

STRUCTURE OF THE BOJfES.

179

curious bone that supports the root of the tongue, and
several smaller ones about the joints of the fingers, which,
like the knee-pan or cap of the knee, are connected
with tendons and act like pullies, we nnay state the
whole number at one hundred and ninety-seven. They
are all constructed upon a uniform plan, being composed
of cellular tissue filled with the cartilaginous and earthy
deposits already described, and a peculiar fatty or oily
substance, called the marrow or medullary matter:* but
from the wide differences observed in their general form
or outline, they have been divided into the long bones
and the flat bones, though there are many which cannot
be ranged correctly under either head.

387. The surface of nearly all the bones is apparently
solid, and approaches, more or less, nearly to the ap-
pearance of ivory. In some places, this plate, or layer,
is nearly half an inch in thickness ; as in the middle of
the thigh-bone ; while in others it is thinner than a w^afer,
and is perforated by many holes of considerable size ;
as on the exterior of the bodies of the spinal bones. In-
ternally, on the contrary, the osseous or earthy matter
is arranged in the form of a network, or large cells,
containing marrow.

388. The bones forming the cranium (321) are, for
the most part, of the flat order (386), varying from one-
eighth to half an inch in thickness. Their solid and
dense sides are called the inner and outer tables of the
skull, and the space included between them is called the
diploe. It is filled with a multitude of small bony cells,
freely communicating with each other, and forming a
spongy-looking mass. Fig. 40 will give Fi^. 40.
you an idea of this arrangement. It re- ^^^^^^^
presents a small portion of one of the flat cTT^^V?^^"*

f r 1 . , Section of Occiput.

bones oi the skull sawed through m the

direction of its thickness. The inner table, which is

thicker than the outer one at the particular part repre-

* This medullary matter has nothing" in common with the medullary
matter forming' the chief part of the brain and nervous system ; see
paragraph 283 ; and this identity of name between such dissimilar
substances, is peculiarly unfortunate.

180

STRUCTURE OF THE BONES.

8ented in the figure, is usually thinner, and always much
harder, bearing a tolerably close resemblance to ivory.

389. In the long bones, the solid walls of the middle
portions of the shafts, where these bones are most slen-
der, are very thick and strong ; but towards the extremi-
ties, which are enlarged, to form powerful joints, the
walls are thin and delicate.

390. On the contrary, the interior of the extremities
is completely filled with small, spongy cells, like the
diploe (388). These cells enlarge in size, and their walls
become less and less perfect as you approach the shaft,
until they form a mere loose network of bony fibres.
Long before you reach the middle of the larger long
bones, you find this network gradually disappearing
from the central line of the cyhnder, spreading itself in
a thin and irregular layer over the thicker surface of the
solid walls of the bone, and leaving a large cavity or

canal within it, called the medullary cavity.
Fig. 41. At fig. 41 you see a longitudinal section of
the thigh bone, in which this arrangement
is clearly shown : a represents the delicate
solid table of the extremity next the knee
joint, filled with its spongy cells of bone;
b, h, shows you the thick, solid walls of the
middle of the shaft; and c, the medullary
cavity. The principal use of the solid
walls and canal, in the middle of the long
bones is, to lessen their weight without
diminishing their strength, where grace and
ease demand that they should not be very
thick. The security of the joints while
undergoing violent exertion requires that
the bones that form them should have a
broad and large surface of contact. If the
bones had been made solid in these situa-
tions, they would have been too heavy for
active motion. Had they been furnished,
like the shaft, with solid walls, and a me-
dullary cavity, the latter must have been
made very large to eflfect economy in weight, while

Section of the
Femur.

STRUCTURE OF THE BOPTES. 181^

the former would have been too brittle, and not suffi-
ciently supported from within to withstand the severe
shocks anci strain to which the joints are continually
liable. For these reasons, the extremities are formed
chiefly of cellular bony matter, which yields a little, and
thus destroys the effect of forces under which the more
solid shaft would break if directly subjected to them.

391. Several different names are applied by anato-
mists to the loose bony matter, resembling the diploe,
which occupies the interior of the bones ; and as you
may frequently meet with them in your reading, it is
well to mention them here, although most of them are,
in some degree, objectionable or partial in their appli-
cation. It is termed the cancelli or cells, the cancellated
structure or cellular structure, and the reticular struc-
ture or network of bone,

392. You have been told that the cellular tissue
forms the foundation, or, to speak more accurately,
that it is the instrument of the nutrition of all the organs
of the body. It can never be wanting, then, in any por-
tion of the bones. In the very earliest stage of their
growth they are entirely composed of this tissue ; and
the only reason why it is difficult to demonstrate its
existence in the most solid parts of the skeleton, is, that
the cells of the tissue are there so completely filled with
the gristle and phosphate of lime thrown out in the
process of ossification, that a membrane so delicate and
transparent cannot be perceived in the mass.

393. In the cancellated structure and the medullary
cavity, the cellular tissue becomes much more obvious.
It lines the cancelli, and fills up the entire medullary
canal ; being every where endowed with peculiar powers
of life, enabling it to secrete the marrow, which fills
these parts as it does the diploe in the flat bones of the
head (388).

394. Even the most solid portions of the bones con-
tain innumerable canals and cells, which only escape
attention by their minuteness. Many of them are suffi-
ciently visible where they have been divided by the saw,
and others may be seen by the aid of the microscope.

182 STRUCTURE OF THE BONES.

In the short and flat bones, and the extremities of the
long bones, these canals pass in all directions through
the walls into the reticulated structure ; but in the shafts
of the long bones they pursue a very oblique direction,
traversing the walls for a great distance before they
enter the interior. When the animal matter is chiefly
destroyed by burning or exposure to the weather, the
bones are apt to break or fall to pieces by scaling off" at
the surface, and this has given rise to the opinion that
they are formed of separate tables, placed one over
another; but this appearance is merely owing to the
direction of the long canals running obliquely through
the harder parts and rendering them weaker in certain
places. These passages communicate freely wdth each
other by means of numerous branches ; so that, in fact,
the solid walls are really composed of a network of
bony matter, difl^ering from that of the extremities and
the diploe only in having the meshes too small to attract
attention. All these passages are lined by cellular tissue
and filled with marrowy as may be ascertained at once
by laying the fresh bone of an animal in the sunshine,
after stripping it of its periosteum. The oily matter of
the marrow will then flow out and collect on the surface
in little drops.

395. The minute vessels that supply the nourish-
ment for the bones, and carry off" the worn-out particles
from them, are branches derived from the vessels of
the periosteum (175). They enter the canals already
described (394), and traverse even the most solid parts,
supplying not only the gristle and earthy deposit, but the
marrow also. They are much more numerous and
larger where there is most of the diploe or cancellated
structure in their interior. They are very small and
comparatively few in number in the shafts of the long
bones, but occur in such abundance near the extremities,
that the walls of these parts are riddled by them like a
sieve. But in those bones that are thick and bulky, and
those that have a medullary cavity within them, we find
one or more larger holes in the most solid part of the
shaft or outer table, to give passage to as many larger

STRUCTURE OF THE BONES.

183

blood-vessels, the branches of which are distributed over
the cellular tissue contained in the reticulated structure
and the medullary canal. These large vessels are chiefly
employed in the secretion of marrow; but when acci-
dents, such as fractures, require them to assist in form-
ing solid bone, they have the power to do so.

39G. As the functions of the bones are entirely passive,
they do not require the sense of feeling, and consequent-
ly their nerves are all received from the nervous system
of organic life. They may be sawn or broken, when
in health, without awakening any consciousness in the
individual. There is a common opinion among the un-
informed, that the marrow is exquisitely sensitive; but
in truth it is altogether incapable of pain. Yet when
inflamed, or otherwise diseased, the bones or the mem-
branes secreting the marrow may be the seat of the
most agonizing suffering.

397. After these remarks, you will be no longer sur-
prised to hear that the bones themselves are sometimes
affected by severe inflammation, abscess, ulceration and

Fig. 42.

Longitudinal Section of the Skull.

184 STRUCTURE OF THE CRANIUM.

other complaints, such as are seen in other parts. They
are truly living organs, and share alike the benefits and
the evils of life ; and you have been informed already
that they may change their character so completely in
some cases as to be no longer bones (164).

398. It is novi^ time to speak of the different portions
of the skeleton, and the manner in which they contribute
to the formation of the frame. And, first, let us consi-
der the bony structure of the head.

Fig. 43.

Side view of the Skull.

399. The cranium, or that bony case which contains
the brain, is composed of eight principal pieces, six of
which belong to it exclusively, and two are so formed
as to assist in constructing the frame-work of the
face also. If you remove from the cranium all the
bones of the face, there will remain a solid box inclosing
a large cavity. In general form, it bears a strong resem-
blance to an Ggg, with the narrow end directed forward.
The lower part of the egg is a little flattened and looks
as though it had been crushed and indented in two
places; first, on a line directly between the ears, and
again, just behind the orbits of the eyes, where it is very

OF THE FRONTAL BONES.

185

much flattened. Fig. 42 will give you a clear idea of
the general form of the cavity and the relative thickness
of the walls, which latter, however, varies much in
different places, as you have been told (388). You
observe that the upper part of the cavity is regularly
and beautifully arched, but that its lower surface or
floor is divided, by the indentations just mentioned, into
three considerable depressions, designated by the letters
g, h, i. As these depressions correspond exactly with
three others on the opposite side of the middle line of
the head, there are, in reality, six such depressions in
the base or floor of the cranium. This should be parti-
cularly remembered, for you will find the fact important
when we consider the structure of the brain, which fills
this cavity entirely.

400. The anterior part of the egg- Fig. 44.
shaped box of bone is called the frontal
bone. It forms the forehead, and in ge-
neral shape somewhat resembles a clam
or scallop shell, standing upon its apex
or beak. You see it in its proper position,
viewed in front, at a, fig. 46, laterally
at a, figs. 42 and 43, and from above
at «, fig. 45. It extends from temple to
temple, and from the eyebrows to a dis-
tance of tw^o or even three inches above
the roots of the hair on the forehead.
Throughout the greater part of this ex-
tent it is pretty nearly uniform in thick-
ness, and possesses every where the
two solid tables and the diploe very
clearly marked (388).

401. But just within the eyebrows we
generally find in the adult, two consider-
able cavities, one on each side (fig. 42, e),
formed by a separation of the two tables,
and an absence of the diploe at this spot.
These cavities are called the Frontal The spinal coidim..
Sinuses. They are usually separated

from, each other by a thin bony partition, which is often

iSii

186 STRUCTURE OF THE CRANIUM.

incomplete, and sometimes wanting. The frontal sinuses
are connected with the cavities of the nose by means of
short canals or ducts passing through the solid wall of
the bone, and they are lined with the mucous membrane
which passes up from the nose through these ducts.
The cavities thus communicate with the external air,
and produce an eflect upon the voice like that which
would result from enlarging the barrel of an organ :
the extent of the reverberation deepens the tone, and, in
connexion with similar cavities in other bones of the
head, they have much to do with the distinction between
the bass voice of man, the tenor of woman, and the
treble of childhood.

402. The frontal sinuses are not formed until mature
age. They are often wanting and generally very small
in woman. Even in man they are not always pre-
sent. They difier very greatl}^ in size in different indi-
viduals ; being sometimes incapable of containing a
drachm of fluid, and at others, though rarely, admitting
many ounces. Though we can generally form some
estimate of the size of the frontal sinuses by examining
the edge of the orbit and the shape of the brow, this
can never be accomplished with certainty ; and we may
be frequently deceived in attempting to judge the form
of that part of the brain which lies over the nose
and behind the eyebrows, by measuring the surface
of the frontal bone. This difficulty has been much
underrated by those cranioscopists who attempt to
apply the principles of phrenology to the judgment
of human character.*

* (To teachers.) — Phrenology is the science which treats of the func-
tions of the brain. It is the highest and most difficult branch of physi-
ology, and is altogether too recondite to form a proper subject for
popular instruction. Something may be said hereafter of its objects and
limits, but nothing of its details. It is proper, however, to mention here,
that it is a purely physical science, and has no connexion whatever with
metaphysics, though its founders and principal disciples have strangely
confused these subjects in such a manner as to lead the incautious stu-
dent toward fatalism and materialism. Believing, as the writer of this
volume does, that Consciousness and Will, the peculiar property of ani.
mals and the simplest elements of mind, are not functions of the organi-
zation, or properties of any portion of the frame, this note seems neces-

OF THE FRONTAL BONES. 187

403. The staggers — a disease not uncommon in the
sheep and the deer — is occasioned by a worm hatched
from the egg of a peculiar fly that lays its eggs in the
nose of these animals. The worm, as soon as hatched,
crawls up the duct (401), and makes its nest in the frontal
sinus. There, the irritation produced by it occasions
horrible pain, and being communicated to the mem.branes
of the brain within, throws the animal into a state of
frenzy, generally kilHng it in a short time. The same
accident has happened occasionally to man. The worm
might be easily destroyed by boring into the cavity, and
filling it with oil. Even the ordinary inflammations of
these sinuses are dreadfully painful, and sometimes very
dangerous.

404. The frontal bone furnishes coverings for the
orbits of the eyes. These consist of two very thin
plates of bone, slightly arched, one of them extending
directly backward from within each of the eyebrows.
These are called the orhitar plates, and in them we find
the two tables of the skull pressed together, so that there
is no diploe in this place. The plates are therefore very
brittle as well as thin, and hence a thrust in the eye
with a small sword is considered a fatal wound ; for
the point passes readily through the orbitar plate into
the brain.

405. By the phrenologist, the frontal bone is believed
to cover the surface of those organs of the brain w^hich
are the instruments of the reasoning and perceptive
(or knowing) faculties of the mind. It is indented,
internally, and particularly on the orbitar plate, by nu-
merous convolutions of the brain — parts that will be
more particularly mentioned hereafter.

eary to save him from the charge of ignorance, where peculiar, though,
he thinks, well-founded views that cannot be discussed in an element-
ary volume, have drawn him into positions at variance with those of
the founders of an important but still nascent science.

Cranioscopy is the art of measuring the head in order to determine
the form of different parts of the brain ; and its perfection or defects do
not necessarily involve the truth or falsity of the principles of phrenology.
They merely affect the application of those principles to the practical
judgment of character.

188

STRUCTUFxE OF THE CRANIUM.

406. Two larae bones connected together along the
middle line of the head (fig. 45, b), form the upper part
and sides of the great arch of the skull. They are
called the paiietal bones. They are seen at fig. 42, b,
fig. 43, b, and fig. 45, b. Except that they are arched in

p-^ 2- all directions, the general

** * form of these bones is near-

ly square. They are thick,
and present the regular ap-
pearance of two tables and
a diploe more perfectly
than any other bones of
the head. At their lower
edges they are bevelled off
sharply where the upper
part of the temporal bones
(to be presently described)
overlap them. The edges
are arched upward, and the
lower and anterior corner
stretches downward to-
Top view of the skuii. wards the angle of the eye
for a short distance. Internally, their surface is strongly-
grooved by the trunk and branches of the two great
arteries of the internal periosteum or dura mater, which
will be described hereafter, and are indented, like the
frontal bone, by the convolutions of the brain.

407. The parietal bones cover the surface of those
portions of the brain which are considered by the phre-
nologists as the insti'uments of the more purely moral
sentiments of the mind.

408. The occipital bone forms the posterior part and
a considerable portion of the floor of the cranium. You
see it represented at c, fig. 42, c, fig. 43, and d, fig. 45.
Its general shape is not unlike a clam-shell without a
hinge, with its narrow beak lengthened out for at least
an inch, and rendered very thick and spongy. This
latter portion of the bone forms the middle portion of
the floor of the cavity of the cranium : it is almost
exclusivelv of a cellular or reticulated structure, having

THE PARIETAL AND OCCIPITAL BONES. 189

but very thin and imperfect solid walls (389). The rest
of the bone is constructed on the same plan with the
bones already described. Its outline, if we except the
beak, — or, as it is termed by anatomists, the cuneiform
or ic edge-shaped j)rocess, — is like a bent lozenge, with
one of its corners directed upward {d, fig. 45), and the
other downward, or rather forward, underneath the skull.

409. Near its lower angle, upon which the cuneiform
process is grafted, we observe a large hole called the
great foramen, (fig. 42, /), through which passes the
spinal marrow, on its way to the canal of the spine,
which will be described hereafter.

410. The inner surface of the bone is divided into
four compartments by a strong, thick, bony cross, glued,
as it were, upon the inner tabic. The upright limb of
this cross runs from the great foramen to the upper
angle of the bone {d, fig. 45), which angle corresponds
with the crown of the head, where the hair divides.
The horizontal limb of the cross winds round to the
lateral corners of the lozenge ; and their place of meet-
ing corresponds exactly with that solid lump of bone
which is felt on the most prominent part of the back of
ths head.

411. This cross gives great strength to the bone, par-
ticularly in the centre, where its limbs meet. This is by
great difference the thickest and strongest part of the
arch of the skull, and is provided with a great quantity
of the diploe, as is seen in fig. 40, which is a transverse
section of the part, and at c, fig. 42, which presents you
with a longitudinal section. The structure of this part,
and that of the frontal bone at the eyebrows, most
beautifully display the wisdom of the Creator in the
minute details of our organization. These prominent
portions of the skull are most subject to blows and to
injury in falls; and were it not for the frontal sinuses
separating the two solid tables or the great abundance
of spongy diploe at the centre of the occiput, which
deaden the effect of concussions, few of us would
reach mature age without suffering from injury to the
brain within from unavoidable accidents.

17*

190

FRONT VIEW OF THE SKELETON.

Fig. 46.

BACK VIEW OF THE SKELETON.

191

Fig. 47.

■

192 STRUCTURE OF THE CRANIUM.

412. The limbs of the cross divide the occipital bone
into four compartments, each of which is somewhat
excavated, so that they form four depressions. The
two lowermost of these correspond with the posterior
depressions of the base or floor of the skull already
mentioned (399). They contain a portion of the brain
regarded by phrenologists as purely instinctive in its
functions. This is so different in appearance, and so
nearly separated from the remainder of the brain by
intervening membranes, that it is called the lesser brain
or cerehelbim, to distinguish it from the greater brain or
cerebrum. The two superior depressions situated above
the horizontal limb of the cross receive the posterior
part of the cerebrum, which is supposed to form the
instruments of the mind in what relates to the social
affections.

413. The greater part of the sides of the cranium
above and around the ears are formed by two bones
called the temporal bones. They are composed each
of two portions very different in structure. The first
portion, called the squamous or scaly plate, seen at
d, fig. 43, and e, fig. 45, is part of the arch of the
cranium. It has the two regular tables of the other
bones, but is hard and brittle, containing very little
diploe. The upper edge of this plate is nearly semi-
circular, and is bevelled away from the inner side until
it becomes quite sharp, giving it a scaly appearance.
This bevelled edge overlaps the margins of the sur-
rounding bones to a considerable distance.

414. The second portion of the temporal bone is
called the petrous or stony portion. It forms part of the
floor of the cranium. In shape it resembles an irregu-
lar triangular prism, lying upon one side, with the oppo-
site angular ridge directed upward towards the brain.
This portion, as its name implies, is formed of very
solid bone, though many very important canals and
cavities exist within it, among which may be mentioned
all the cavities for the accommodation of the organ of
hearing, the canal for the passage of the principal
artery of the brain, the passage for the lube conveying

OF THE TEMPORAL AND SPHENOID BONES. 193

arr from the throat to the drum of the ear, the closure
of which causes incurable deafness, and the canal
through which the nerve commanding the motion of
the muscles of the face pursues its course.

415. The petrous portions of the temporal bones run
obliquely forward and inward, nearly to the middle of
the iloor of the skull. Their angular ridges seem like a
continuation of the horizontal limb of the internal cross
of the occipital bone, and with it, form nearly a circle
around the posterior depressions of the floor of the
cranium, marking the dividing hne between the cere-
bellum and the cerebrum ('^2).

416. Just behind the ear you feel a large and pro-
minent piece of bone pointing downward. This is the
posterior angle of the temporal bone. It contains a
number of large cells communicating with the drum of
the ear, and of course admitting the air. If the tube
running from the drum of the ear to the throat were
closed (414), we might restore the lost hearing for a
time by boring into these cells. This has been done in
a few cases, but surgeons have not yet been able to
keep the wound open for any great length of time.

417. A long and narrow bridge of bone springs from
the temporal bone just before the ear, and unites, at its
extremity, with the bone of the cheek. A principal
muscle closing the lower jaw arises from the temple,
and passes under this bridge. Just within the base of
this bridge is found the cavity of the joint of the lower
jaw.

418. Of the two remaining bones of the cranium,
which assist also in supporting the face, the largest is
called the sphenoid hone. In form it is compared to a
bat, with its body, legs, and wings, but it is unnecessary
to attempt a particular description of it. The body
forms the centre of the floor of the skull. It is hollow,
containing one or two very large cells (fig. 42, d)^ with
thin and delicate walls. These cells communicate with
the throat, and produce an influence on the pitch of the
voice (401). This bone stretches entirely across the

194 STRUCTURE OF THE CRAMUM.

skull ; forms a great part of the floor of the middle
depressions of the base of the cranium, and also the
posterior edges of the anterior depressions (39*J). It
also furnishes a broad plate to each temple, which lies
between the edges of the temporal bone behind, and the
frontal bone before.

419. The only bone remaining to be noticed is called
the ethmoid hone. It is chiefly concerned in constructing
the upper part of the outer sides of the nostrils, where it
forms a nuuiber of cells with their partitions, over which
the branches of the nerve of smell are distributed. Two
considerable portions, which are situated on opposite
sides of the nose, are joined together by a very thin
horizontal plate called the cribriform plate, forming a
roof for the nose, and separating that cavity from the
brain. This plate is completely riddled by minute holes
that give passage to the branches of the nerve of smell,
as they leave the cavity of the cranium. It is very
small, and lies between the orbitar plates of the frontal
bone (404), before the front edge of the sphenoid bone,
and immediately behind the root of the nose. A severe
blow on the last named spot may crush this cribriform
plate, which is not much thicker than paper, and the
consequence is generally fatal.

420. The flat bones of the skull are connected to-
gether at their edges by tooth-hke projections which
interlock with each other, forming a zigzag line called
a suture ; so that the arch formed by them is nearly as
solid as if constructed of a single piece, and the bones
cannot be detached without breaking some of the teeth.
In fig. 45 you see several of the principal sutures : «, a,
represents that which separates the frontal from the
parietal bones; h, that dividing the parietal bones from
each other; c, c, that which lies between the occipital
and the parietal bones; and e, the suture between the
temporal and parietal bones.

421. The cranium, thus constructed, is covered by
the periosteum externally, and by the dura mater within.
Between these membranes the cartilaginous and earthy
matter of the bone are secreted together, and not, as

OF THE CRANIAL BONES IN CHILDHOOD. 195

in other parts of the skeleton, successively. But during
childhood the bones of the skull ren:iain, for a time, com-
paratively soft and flexible; so that they may be bent or
indented without breaking. Certain savages have a cus-
tom of binding flat boards upon the heads of children,
in order to prevent the skull from growing in particular
directions. The bones, by their softness and flexibility,
yield gradually to this pressure ; and when, in after life,
they become firm and brittle, the head appears per-
manently deformed. The different portions of the brain
readily accommodate themselves to such changes in
early life ; and the functions of those all-important or-
gans are not materially affected by these superstitious
habits. Some erroneously suppose that these alterations
in the form of the skull are believed by phrenologists to
modify very seriously the powers of the mind, and a
notion of this kind is excusable even in a teacher of the
science, if he be not well grounded in the principles of
physiology. The changes alluded to only serve to ren-
der it much more difficult to judge of the form of differ-
ent parts of the brain from that of the outside of the
cranium ; and as they are sometimes produced by acci-
dent as well as by art, he should be a thorough physio-
logist who undertakes to decide such questions with even
tolerable certainty.

422. When, in infancy, the bones begin to ossify, most
of those of the cranium are formed of many pieces.
Thus, the two sides of the frontal bone are separate
from each other, and the edges do not come in contact.
Now and then it happens that the ossification goes on
too slowly in the principal portions, and nature, seem-
ingly in haste, sets about secreting bone in one or more
places in the intervals. Each of these spots being the
centre of a separate ossification, there result as many
little accessory accidental bones, if you will allow me
such an expression. When completed, these bones are
attached to the larger ones by sutures, as these latter are
to each other. Two such accessory bones are seen at
d, d, fig. 45, between the occipital and parietal bones.

423. In very young children, the bones of the skull

196 STRUCTURE OF THE CRANIUM.

are very incomplete ; their edges being widely distant,
especially at the corners, where the head is soft to the
touch; and you can plainly see or feel the pulsations of
the brain within. At these places which correspond
with the position of the sutures, the brain is enclosed
simply by the periosteum and dura mater, with a httle
oose cellular membrane between them, designed to re-
ceive the bony deposite as the child advances in age.

424. To the arrangements just described (421, 422,
423), we are often repeatedly indebted for our continued
existence before we complete the first year of life. Were
it not that the skull can yield, and the edges of the bone
approach or separate from each other by stretching or
pressure, every little jar from a fall or a blow would be
felt in full force by the soft and delicate brain ; and in
many cases of unavoidable accident, this part would be
torn. As it is, even a fracture of the skull is much less
important to a young child than to a grown man ; and
the former will often survive a fall that would be fatal
to the latter. In fractures with depression of the skull,
in childhood, if the pulsation of the brain should not
elevate the pieces to their proper level, the rest of the
head is immediately enlarged to accommodate the brain;
but, in youth or manhood, the patient dies by the pres-
sure, or lives to be subject to convulsions from the con-
tinual irritation of the brain.

425. When dropsy of the brain occurs in very early
life, the cranium may become enlarged till it nearly
equals the chest in its dimensions ; yet the child may
sometimes live to maturity, though generally in a state
of idiocy. But when the same complaint happens in
persons over five years of age, it is speedily fatal ; be-
cause the bones cannot increase in size rapidly enough
to prevent fatal pressure on the brain.

426. It is now well ascertained that the cultivation of
the mind slowly enlarges and changes the shape of the
cranium, even after maturity; and it is equally well
known that the bones of the head generally contract
upon the brain as it becomes emaciated by age, though,
in some few rare cases, they are increased in thick-

ARTICULATIONS OF THE CRANIUM. 197

ness instead of being diminished in size. You cannot
be surprised at this fact, When you know that all the
bones will grow when the muscles attached to them are.
much and properly exercised, and that they dwindle
away, like the muscles, when unemployed. These things
are but so many evidences of the truth of the law that,
the more the function of any organ is exerted, unless
it becomes exhausted, the more active will be its nutri-
tion. Let this be a stimulus to you in the endeavour
continually to strengthen, by exercise, all those useful
powers of body and mind in which you find yourself
deficient. All such endeavours are like investments at
compound interest; — the income is continually added
to the capital.

427. The form of the cranium, arched in all direc-
tions, except on its under surface, where it is protected
from injury by the neck, gives it all the strength of a
bridge. But you know that when a great weight is
placed on the centre of a bridge, it is more likely to
give way at the extremities than at the spot where the
weight presses ; thus a heavy blow or fall on the head
often breaks the skull, not on the part which directly
receives the injury, but at the sides of the head, where
we should find the abutment of the bridge. But this
arrangement is a proof of the beautiful economy of na-
ture, for it is that which gives the greatest degree of
strength with the least amount of material. A sharp,
quick blow, with a small, heav}^ instrument, such as a
hammer, or steel cane, will generally break the skull at
the spot which receives it ; as a cannon ball, or a frag-
ment of a blasted rock, will pass through the plank of
the bridge without shaking the abutment.

428. The cranium, constructed as has been described,
sits upon the summit of the column of the spine, fig. 44,
page 185, with the two uppermost bones of which it is
articulated in a very curious manner. On each side of
the great occipital foramen, I, fig. 42, there is a projec-
tion of spongy bone, covered with cartilage, forming a
joint, with a corresponding depression at the side of the
first spinal bone. This joint permits the head to be

198 ARTICULATIONS OF THE CRANIUM.

Raised, to rock, or to bow forward till the chin nearly
touches the breast. But if the same joint had been so
constructed as to allow the head to turn upon it freely
from side to side, it would have been too liable to dislo-
cation, an exceedingly dangerous accident that has
sometimes happened when the head has been very sud-
denly and violently turned round. The dislocation can
only happen upon one side at a time; and w4ien it occurs,
the face is turned towaixis the corresponding shoulder.
To restore it to its natural position again, is an opera-
tion that few surgeons would have the hardihood to at-
tempt ; for the slightest unsteadiness of hand might be
instantly fatal to the patient, by compressing the spinal
marrow as it descends through the foramen. In order,
then to allow the head its proper freedom of circular
motion, another arrangement is necessary.

429. The uppermost bone of the spine is little more
than a bony ring, with cavities on its upper surface to
receive the projections by the side of the occipital fora-
men mentioned in the last paragraph, and with two
similar projections on its under surface, designed to form
a joint with the second bone of the spine.

430. To prevent repetition it may be well to inform
you that such prominences of bone as are designed to
assist in forming the movable joints are called condyles.

431. The second spinal bone of the neck is not a
simple ring, but is constructed like the other pieces of
the spinal column, fig. 44, w-ith a large mass of spongy
cellular bone in front, called its body, supporting an arch
or bridge of bone on its posterior side, to surround and
protect the spinal marrow. A long round piece of bone
projects upward from the body, passing through the ring
of the first spinal bone, and rising to the level of the
occipital foramen. This piece is covered with cartilage
both in front and rear. In shape it resembles a round
tooth, and this circumstance gives it the name of ver-
tebra dentata or toothed vertebra, while the uppermost
bone is fancifully styled the ailas, from its dignified
office in giving immediate support to the head.

432. The tooth-like process of the vertebra dentata is

MOTIONS OF THE HEAD. 199

held firmly against the anterior part of the ring of the
atlas by a very strong ligament stretched across the
ring behind it, and it is securely attached to the atlas
and the occipital bone by several curious ligaments
which keep it in place, w^hile they permit the head to
bow and rock to a certain extent, and to perform its
other necessary motions.

433. When the head turns from side to side, the atlas
travels with it, and the condyles by which it is articu-
lated with the vertebra dentata are so constructed as to
permit this motion to be carried to a certain distance
with safety.

434. But none of the motions of the head can be car-
ried very far forward, backward, or to either side,
without the aid of all the spinal bones of the neck ; and
on great occasions, the whole body must be called into
action. Were more motion allowed to the immediate
articulation of the head with the spine, the spinal
marrow would be in constant danger of being, crushed
by the pressure of the tooth-like process of the second
vertebra; which is the cause of death in the fatal
attempts to replace a head that has been dislocated.

435. The muscles which support the head and give it
motion are very numerous ; and as the head always has
a tendency to fall forward by its weight, those which
draw it backward are larger, stronger, and acquire more
tone from habitual exercise.

436. The muscles of the head originate from the
spine, the shoulder-blade, the collar-bone, the breast-
bone, and the ribs. All the motions and peculiar condi-
tions of these various parts must influence the attitude
of the head. For example ; an inflammation of the
spinal periosteum or rheumatism of the shoulders, com-
pels a patient to stoop, because the tone of the muscles
that raise the head is diminished by this disease, and
their action rendered painful. A palsy of one side
causes the head to be carried toward the opposite
shoulder, for the same reason. Changes of the whole
figure and serious injury to health often result from the
long continued operation of these seemingly trivial causes.

200 BONY STRUCTURE OF THE FACE.

But this subject will be more properly discussed in a
future chapter.

437. As we are studying physiology and not anatomy,
we may now relinquish the details of the structure of the
cranium, and it will not be necessary to dwell long on
that of the face, as it illustrates no very important prin-
ciple necessary to my scheme.

488. The bony structure of the face is very complex ;
being composed of fourteen bones, exclusive of the teeth,
■which are thirty-two in number. You would learn
more of these bones in one hour from an examination
of the real skull in the hands of a well instructed phy-
sician, than in the study of description, even with the
aid of the best plates, for a month ; and I shall confine
myself to a few remarks upon the jaws and teeth.

439. The upper jaw is composed of two bones, united
in the middle, fig. 43, h. They form two-thirds of the floor
of the nose, the roof of the mouth, or the bony palate,
a part of the side of the nose, and a considerable share
of the floor of the orbit of the eye. They also aflford
the chief support to the other bones of the face; yet
they each contain a very large cavity communicating
with the nose, lined — like those already noticed in cer-
tain bones of the cranium — with mucous membrane,
and constituting a portion of the surface of the body.
The walls of this cavity are very thin in many places ;
so that were it not that we habitually and instinctively
shield the face from danger, they would be very liable
to fracture from accidental violence ; but injuries of this
kind are exceedingly rare.

440. Several important nerves of sensation pass
through small canals in the walls of the upper jaw, as
others, already mentioned, penetrate the solid portions
of the temporal bones (414). When the periosteum
lining one of these canals becomes inflamed, there is
not room enough to accommodate the swelling thus
produced, and the enlarged membrane, pressing forcibly
upon the nerve, occasions intense pain. Many cases of
that formidable disease called the tic douloureux occur

STRUCTURE OF THE TEETH. 201

from this cause. Rheumatism is often an affection of the
periosteum, and frequently gives rise to the complaint
just mentioned. All the nerves which pass to the teeth,
whether in the upper or lower jaw, are inclosed in
canals of solid bone ; and in cases of cold, or disease of
a tooth, inflammation may be extended to the perios-
teum of these passages. All the teeth in either jaw
may be thus affected with toothach, and the sufferer
or the dentist may be unable to discover exactly where
the evil commences.

441. There are sympathetic connexions between the
nerves of the teeth and many of those of the ear, the
muscles of the face, or even the eye. From this circum-
stance, injuries or decay of the teeth give rise, in some
rare cases, to blindness, deafness, or palsy of the cheek.
It is impossible to explain these connexions except to
profound anatomists ; but you may judge of their im-
portance when I tell you that I have seen the whole
cheek and the lower eyehd palsied, so that the mouth was
distorted, the eye could not be closed, and the hearing
was much impaired, by a slight and unavoidable acci-
dent in the extraction of a tooth. Fortunately, the alarm-
ing consequences resulting from this cause are not very
lasting : I have never known any of them to continue
beyond a few weeks. When they are occasioned by
decay, by rheumatism, or by diseases of the jaw, thgy
may endure as long as the cause on which they depend.
Extraction of a few carious teeth has been known to
cure a deafness of long standing, or to improve defective
vision.

442. The teeth are not constructed upon the same
principle with the other bones : each of them seems to
be an osseous incrustation upon the surface of a nervous
papilla (350). In some animals they grow for a long
time after they are in use, like a hair (356), by depo-
sition of new layers upon the root. This is the case
with the tusks of^ the elephant, the boar, &c. ; but they
differ from hair and other appendages of the cuticle in
possessing vitality and sensation in their very substance.
This has been denied by most writers ; but every dentist

'l7 '

202 STRUCTURE OF THE TEETH.

knows that the diseased bone in a carious tooth is
sometimes exquisitely sensitive under the action of an
instrument that does not approach the nerve. Moreover,
I have been convinced by experiment, that in heahh a
tooth perceives, obscurely, what part of its surface is
touched by any foreign body. Blood-vessels and ner-
vous matter exist in abundance within the cavity and
" pulp" of every tooth ; but have not been traced into
the soHd portions.

443. In man the teeth are all constructed within little
membranous sacs, bedded in portions of soft spongy
bone forming the margins of the jaws, and called the
alveolar or socket processes. When the body of a tooth
has reached its full dimensions, the membranous sac
containing it secretes, over its upper surface and around
its sides, what is called the enamel. This^ though re-
sembling in its chemical structure the earthy matter of
bone, contains very little, if any, animal matter. It crys-
tallizes upon the bone beneath it, and becomes so hard
that it is difficult to act upon it by tools of the hardest
steel. It is utterly devoid of life or sensation, though
it transmits impressions to the bone and nerve beneath,
as the cuticle does to the papillae of the sense of
touch.

444. When the body of the tooth has been con
structed, the root begins to grow, in the form of one or
more fangs, and contains within it a branch of the nerve
with the necessary blood-vessels, like the bulb of a hair.
The junction between the fangs and the body is called
the neck. It is narrower than the neighbouring parts
of the organ. The periosteum lining the socket doubles
upon itself, and envelopes the fangs or roots as high as
the neck, where it adheres closely ; and the enamel de-
scends from the crowai of the tooth to the same spot. As
the roots grow, the crown is thrust outward from the
socket, the summit of the secreting sac is absorbed, the
gums covering the part are removed by the same pro-
cess, and the naked tooth appearing, soon rises to its
proper height by a process somewhat resembling that
which forms the hair and nails. The business of nutri-

STRUCTURE OF THE TEETH.

203

tion then ceases in the tooth, and it stands unchanged
until disease, accident, or the progress of age removes it.

445. When the teeth of man are worn down by use
until there is danger of the cavity being opened, new
bone is secreted within the part ; and sometimes in old
persons the cavity becomes completely filled in this
manner ; but the new bone thus formed, is often so ten-
der to the touch that, when irritated, it becomes painful,
and is mistaken for genuine toothach. The same mis-
take is often made when the periosteum is inflamed,
though the teeth may be uninjured. Both these forms
of disease may be generally cured by a treatment similar
to that required in other local irritations. You perceive,
then, that a good dentist should be also a well-informed
medical man ; and that his profession is one of more
dignity than is commonly supposed.

446. We often hear an operator blamed for "break-
ing the jaw" in extracting a tooth. The form of the
roots of many teeth is such that this accident cannot be
avoided ; but it is altogether unimportant ; for the teeth
are seated in the spongy alveolar process, and never
penetrate the firm bone. When the socket is broken,
and the piece removed, the patient is sometimes the
gainer; for, after the removal of the organ, the socket
is always absorbed ; and its destruction is hastened by
the fracture. It is this absorption of the alveolar process
that occasions the approximation of the nose and chin
in very old people ; and, as it sometimes takes place
before the teeth decay, their support may be thus under-
mined, and they may fall out in a sound condition. Ail
this tends to prove the general law that the moment
parts cease to be exercised sufficiently they begin to di-
minish in strength ; and when they become unnecessary
they are removed.

447. The shedding of the milk-teeth, or the set that
first appears in infants, resembles in some respects the
annual shedding of ihe horn in the deer and other ani-
mals. A new tooth is formed in a new sac beneath the
old one, and the connexions of the latter are absorbed,
until it is pushed off from the gum, or, until we extract

204 STRUCTURE OF THE TEETH.

it to relieve nature and promote con:ifort, as the stag
rubs off his useless honours at certain seasons by push-
ing them against, a tree.

448. The language of the teeth teaches us the utter
folly of the dreams of certain empirical enthusiasts who
would persuade us that rluty or health should confine
mankind to one particular species of food, and it equally
exposes the impropriety of many habits common in fami-
lies, that prove destructive to the health of children.

449. The four front teeth in either jaw are called
incisors or cutting teeth. They are constructed like
those of all quadrupeds that graze or subsist upon fruits
and vegetable matter exclusively. They are not suffi-
ciently strong to tear the tougher meats, nor are their
crowns broad and flat enough to grind the larger and
harder roots and other vegetable food. They are the
first to appear in childhood ; thus most clearly showing
that when the natural food of infancy becomes insuffi-
cient in itself to support the frame, animal food was not
designed iinmediately to supply its place. When these
teeth fall, they are replaced, in the growing youth, by
others of the same kind, but much larger and stronger
than their predecessors ; proving to all who study the
beautiful, simple, and consistent designs of Providence,
that a vegetable diet, to a certain extent, is still neces-
sary to the health of man.

450. Next in order, after some time, appear four
temporary grinders — one on each side of each jaw —
fitted for the mastication of little else than vegetable
matter. At a still later period the canine or eye-teeth,
sharp and conical and made for tearing, are added to
the list. These resemble the teeth of the beasts of prey
which subsist entirely on animal food, and whose jaws
are armed with such instruments alone ; being divested
of proper incisors, and provided even with grinders of
which the summits are studded with conical eminences
that act with greater force but in much the same manner
as the sharp-pointed front teeth. You may readily and
safely examine these teeth in a tame cat or dog. After
the canine teeth, four other temporary grinders, of the

DIETETIC INDICATIONS OF THE TEETH. 205

same character with those mentioned above, make their
appearance, and the set of infant teeth is perfected to
the number of twenty.

451. The proper time pointed out by nature for per-
mitting a child to partake of the ordinary meats of the
table, is the period when the canine teeth have reached
their perfect condition.

452. All the infantile teeth are lost in early life ; but
these are regularly replaced by others of similar charac-
ter and greater size, while, by the addition of twelve
more grinders, the number is raised, in manhood, to
thirty-two.

453. Now the existence of the canine teeth through
life furnishes evidence that an exclusively vegetable diet
was not designed for man, and at once betrays all the
absurdity of those strange doctrines which reduce the
natives of India to feebleness of mind and body, and are
now effecting the same lamentable consequences among
certain enthusiasts in our own enhghtened land. Even
the form of the human grinders furnishes another proof
of the same fact. Their crowns are provided with
eminences of an intermediate character, between those
of the grazing animals on the one hand and the beasts
of prey on the other ; being equally well fitted for
crushing the esculent roots and the flesh of animals. So
unerring is this language of the teeth throughout the
whole range of quadrupeds, that if you were to present
an experienced naturalist with the jaw of an unknown
animal, he would at once inform you correctly of the
nature of its food.

454. Were I treating of the art of preserving health,
I might profitably enlarge upon this subject, but in a
volume on the elements of physiology, I must leave the
application of the principles mainly to yourselves.

455. There exists an evident sympathy between the
stomach and the teeth ; and any disorder of the one is I
dangerous to the health of the other. A want of clean-
liness and daily attention to the former, or the injurious
trifling of an unskilful dentist, is not only destructive of
beauty, but increases the liability to dyspepsia with all

206 STRUCTURE OF THE SPINAL COLUMN-.

its train of suffering, gloomy feeling, misanthropy, and
irritability of temper, rendering life miserable, even if it
be not curtailed by the imperfection of mastication — the
first and most important step preparatory to digestion.
On the other hand, the constant indulgence in the eating
of indigestible and doughy cakes during childhood, the
iniquitous conduct of certain parents in encouraging the
use of stimulating drinks at the same tender period, and
the ridiculous, if not criminal habits of diet adopted in
gay society, are very frequently destructive of the teeth.
Need we be surprised then that dyspepsia and bad teeth
are so increasingly common as to leaduncourteous travel-
lers and men of the olden time to regard them as pecu-
liarly characteristic of the American climate or the
degeneracy of the times ?

456. Although the mere mechanism of the head would
furnish an ample subject for this entire volume, it is now
time to glance over the remainder of the skeleton. In
doing so, I shall avoid all unnecessary anatomical detail,
but I must beg your undivided attention to the few re-
marks of this character which cannot be avoided.

457. TJie spine, which is the most important part of
the frame-work of the trunk, extends from the lower
part of the loins to the head, along the back of the body,
w^here it may be plainly felt throughout its entire length.
It is composed of twenty-four pieces of bone called
vertehrcB. It forms a column somewhat, but not quite
regularly conical ; and instead of being perpendicular, it
has several curvatures, giving it somewhat the form of
the letter S, inverted; as you see in fig. 44, page 185,
which represents it detached and in profile. When you
regard it in front or rear, it appears straight.

458. Of the twenty-four vertebrae, seven belong to the
neck, and are called the cervical vertehrce, — twelve to
the back, called the dorsal vertebrcB, — and five to the
loins, called the lumbar vertehrcc. The cervical part of
the spine curves gently forw^ard, to bring it more nearly
under the centre of gravity of the head, which it sup-
ports. The dorsal portion sweeps widely backward, to
enlarge the cavity of the chest: and the lumbar portion
again projects anteriorly, to restore the balance.

STRUCTURE OF THE SPINAL COLUMN. 207

459. The conical form of the spinal column is princi-
pally owing to the shape of the bodies of the vertebrae
(431), which constitute by far the largest portion of each
of these bones, except the atlas, which has no body,
(429, 431).

460. Fig. 48 represents one
of the cervical vertebra, and
will serve us to explain their
general form and their several
parts. At a, you see the spongy
body of the bone, with its up-
per surface slightly excavated,

but nearly flat. The under sur- ^^^^KIBJS^Pc
face is also flattened. From y/^ ^^^ffr ^^ ^
the sides of the body you see a cc

bridge of bone encircling an A Cervical Vertebra.

nnpn «mpp marlrpri ir Thi<a «• The body. h. The forked spi-

Open space, maiKea ^^. i'llS j^^^gp^^P^gg c. c. Transverse pro-

is a portion of the lont?- canal cesses, a. a Holes for the cervical
.' , 7 111 c- arteries— also grooves for the spi-

runnmg the whole length OI nal nerves, e. e. superior condyles.
4.V • 1 * J .1 L f f Process of bone supporting the

the spine, completed partly by .^..Jerior and inferior condyles." g.

the bones and partly by the sur- Part ofthespinaicanai.
rounding soft parts, for the ac-
commodation of the spinal marrow. At the abutments
of this bridge you perceive two smooth surfaces (e, e,)
seated upon jutting portions of the bone (/, /). These
planes are coated with cartilage. They are the con-
dyles (430) for the articulation of this vertebra with the
next one above. On the lower part of the same por-
tions of bone (/,/') are two corresponding surfaces,
which are the condyles for the articulation with the next
vertebra below. From the sides of the abutments of
the bridge arises a bony prominence on either hand
(c, c,), with a hole or foramen {d, d,) passing through it.
These prominences are called the transverse processes,
and are chiefly designed to give origin or attachment to
the muscles of the back. The holes in them are pecu-
liar to the cervical vertebra, being intended to give a
secure passage to a considerable artery of the brain,
called the vertebral artery, on its way to the cavity of
the cranium. At b, you observe a portion of bone pro-

208 STRUCTURE OF THE SPINAL COLUMN.

jecting from the middle of the bridge. Each vertebra
is furnished with a similar process, and all these bones
may be counted with the finger passed along the back,
where they often occasion visible elevations. They are
called the spinous processes, and, like those previously
mentioned, they furnish origin and insertion to muscles
of the back. The fork at the extremity of the processes
is peculiar to the cervical vertebrae. Except in this last
respect, and in the presence of the holes through the
transverse processes, all the vertebras, except the atlas,
resemble each other ; but the comparative bulk and
direction of the different parts are very various in dif-
ferent parts of the spinal column.

461. The articulations of the condyles of the verte-
brae are altogether insufficient to support the column
securely w^ithout further aid ; and to meet this difficulty,
the bodies of these bones are joined together by inter-
mediate rings of a peculiar substance, partaking of the
nature both of liojament and cartilage. This elastic sub-
stance acts like a cushion between each pair of verte-
bras ; and while it allows the column to bend in all direc-
tions, as far as the bones will permit, it is softer, and
almost semi-fluid, in the centre of the column, and be-
comes firm and more fibrous towards the circumference
of the bodies of the bones. The middle of each of these
cushions acts like a pivot, and the circumference, like a
ligament, to prevent excessive motion. Though these
rings of elastic matter are not exactly similar in their
organization to the articular cartilages, — being more like
the gristle of young bone mixed with fibres of perios-
teum,— they are known to many by the rather inaccurate
title of intervertehral cartilages. The substance of which
they are composed is called fihro-cariilage.

462. The spinal fibro-cartilages are gradually com-
pressible to a certain extent, even by the weight of the
body, and consequently, a tall man sometimes measures
nearly an inch less in height in the evening than he does
in the morning, a little diminution of distance between
each pair of vertebra taking place from pressure when
the body is erect, and being regained by elasticity in the

STRUCTURE OF THE SPINAL COLUMN".

209

reclining posture. Tlie emaciation of these rings, from
detective nutrition in old age, is one of the causes of the
diminished stature of elderly people ; but this is much
increased by a similar change in the bodies of the ver-
tebras themselves.

463. The spinal column, with its bones thus connected
by regular joints between the condyles, and by interver-
tebral fibro-cartilaginous rings, is strengthened by very
numerous ligaments, passing not only from the body of
one bone to that of another, but also between the edges
of the transverse and spinous processes and the sides of
the bridge of bone (460), both within and without the
rings (fig. 48, g), formed by these parts. These rings,
and the ligaments just mentioned, form one great canal
for containing the spinal marrow, and the origins of
most of the nerves of sensation and voluntary motion.
It is called the spinal canal, and extends throughout the
entire length of the column, from the great occipital
foramen (409) to the last lumbar vertebra. This canal
is, in fact, a continuation of the cavity of the cranium,
being lined throughout by the same membrane that en-
velopes the brain.

464. The number of bones forming the spine is of the
utmost importance to the safety of life; for, if the spinal
marrow be seriously injured, the parts receiving their
nerves from below the seat of injury are instantly pal-
sied, because the nervous communications with the brain
are thus destroyed. The higher the point injured, the
more important the organs rendered powerless ; and if
it be near the upper extremity of the column, speedy
death must follow ; for you can readily perceive that
if the muscles of the chest are paralyzed the patient
cannot breathe, and the nerves supplying these muscles
spring from the upper part of the spinal marrow. Now
it is absolutely necessary that the spine should bend in
all directions to a considerable extent, and that it should
even be capable of twisting upon itself in order to allow
the person to assume the various requisite attitudes. If
any of these extensive motions were performed at any
one spot, the shape of the spinal canal would be so far

210 STRL'CTURE OF THE SPINAL COLUMN.

changed in that place that the spinal marrow would be
inevitably and tatally crushed. But, by distributing these
motions through a long series of joints, nature accom-
phshes the changes far more gracefully by a gentle cur-
vature that does not materially alter the form of the
canal or endanger its contents.

465. The cervical vertebrte require extensive mobi-
lity in all directions to accommodate the head ; and the
lumbar vertebrae have considerable powers, both of
flexion and rotation. The dorsal vertebrae, on the con-
trary, have scarcely any motion, for their spinous pro-
cesses point very obliquely downward, cover each other
like the shingles of a roof, and even interlock themselves
by means of a ridge on their upper surface and a groove
on the under side. In order to furnish additional secu-
rity to the spinal marrow, the spinal canal is made pro-
portionately very large in the neck, where the extent of
motion is greatest, — large in the loins, where it is still con-
siderable,— and quite small in the dorsal region, where it
scar cell/ exists. How beautiful is the mutual fitness of
all parts of the complex frame!

466. In those unfortunates who labour under decay
of the bodies of the vertebras, producing certain de-
formities of the spine, the spinal marrow is in great dan-
ger; and weakness, if not palsy of the lower extremities,
results. When these cases recover, as they sometimes
do, the ligaments, and occasionally the fibro-cartilages
around the diseased vertebra?, are converted into bone,
so that several pieces of the spinal column become one
piece, and the proper motions of the part are for ever
destroyed. The same thing may occur in old age.

467. The nerves which go off" from the spinal marrow
(292 — Fig. 37), pass through small orifices in the liga-
mentous and membranous lining of the spinal canal,
and are accommodated in their progress by correspond-
ing notches in the upper and lower edges of the abut-
ments of the bridges of bone that confine the marrow.
They are seen in Fig. 48, page 207, and are designated
by the dotted line continued from d, across the hole for
passage of the vertebral artery (460). These notches

OF THE RIBS AND THEIR CX)NNEXI0NS.

211

enclose spaces much larger than the nerves which oc-
cupy them, so that in health they are not endangered
by the motions of the spine : but when the periosteum
of the vertebra becomes inflamed and swelled, in rheu-
matism or other diseases, the nerves are often most
painfully compressed, and, perhaps, irritated. Accord-
ing to the nature of the disease and the particular fibres
most afl^ected, we may have a neuralgia of the spine,
spasms of the muscles, or palsy, with or without pain in
the part affected. You have been told of the connexions
between the spinal nerves and those of organic life,
through the medium of the sympathetic nerve (304).
Now the fibres of the latter which communicate with
the spinal nerves are often interested in diseases of the
soft parts about the orifices through which these nerves
leave the spinal or vertebral canal. Hence, disorders
of internal organs often connected with affections of the
periosteum and the fibrous tissues around it; and the
most profound knowledge, coupled with sufficient expe-
rience, is required to
trace the hidden chain
of relation between
complaints seemingly
so dissimilar.

468. It is needless to
describe particularly
the general appear-
ance of the ribs. A
glance at either of the
figures of the skeleton,
or at Fig. 49, which
represents the bones
of the chest, will give
clearer ideas than
pages of description.
The ribs are twelve in
number on each side.
They form curious
double joints with the
spine, being articulated

Bones of the Cliest.

212 BONY STFxUCTURE OF THE THORAX.

with the bodies of the dorsal vertebrse by a small head
on the extremity, and with the transverse processes by
a smooth prominence at a short distance from the head.
These joints permit them to rise or fall at their anterior
ends, but confine them to a fixed position posteriorly.
They do not encircle the entire circumference of the
chest : for, in front of that cavity you see the slcrnum or
breaslhone, occupying the middle portion of its walls.

469. The bony portions of the ribs do not reach the
sternum, but you observe in Fig. 49, a white portion
extending from the extremity of each rib towards the
latter bone. These are called the cartilages of the ribs,
but they are really composed of bone in that condition
in which it is found in some parts of the skeletons of
children, and in the whole osseous system of certain
fishes (159). The flexibility of these cartilages permits
the ribs to rise and fall in the act of breathing ; and as
the sternum is supported upon them, as if on springs, it
shares in all their motions.

470. Sometimes, in old age, the cartilages of the ribs
become ossified, and their motion is then destroyed.
You wdll naturally ask how the individual can breathe
under such circumstances. The explanation is the more
important, because a silly fashion or criminal vanity
often leads the young and beautiful to imitate this de-
formity of acre by artificial means. I shall enlarge upon
this subject hereafter.

471. The sternum (Fig. 49, a), is composed of several
pieces in early childhood, but rarely fails to become
united into one, before the growth of the frame is com-
plete. It extends downward from the throat to the
bottom of the chest, in front of the lungs and heart. In
general form, it resembles the blade of an antique Roman
sword, placed with its hilt at the hollow of the throat,
and its point at the pit of the stomach. It is tipped
with gristle at its lower extremity, which is called by
anatomists, the ev si form or sword-shaped cartilage. The
angles of the hilt of the sword support the inner extremi-
ties of two long and slender bones of the shoulder, which
you can readily feel in your own person stretching along

OF THE CLAVICLES AND STERXUM. 213

the front of the base of the neck (Fig. 46, /i,-r-Fig. 47,
e, pages 190, 191). These are called the collar hones or
clavicles ; they form the only bony connexion between
the superior extremities and the trunk.

472. The sternum appears suspended from the carti-
lages of the seven superior ribs (Fig. 49) : The three
next ribs are attached by their cartilages to that of the
seventh ; and the two lowermost are merely tipped with
gristle, and are connected with the sternum only by
muscular fibres. The superior extremities are sus-
pended upon the sternum by means of the clavicles
(471) ; and the articulations of the ribs being moveable
behind at the spine, the w^eight of the whole chest and
arms tends to drag the ribs downward and contract the
chest.

473. The few muscles attached to the spine and the
posterior ends of the ribs near the joints, are too weak
to resist the whole w^eight of the chest ; and those
of the breast, though they may draw the ribs nearer
together or toward the shoulder, cannot, of themselves,
elevate the chest, because they are attached at both
extremities to moveable parts — that is, to the ribs and
to the shoulder. Now, the chest must be elevated dur-
ing inspiration, or the man cannot breathe ; and it is
evident that this can only be effectually accomplished
by means of bands or props running from the chest or
shoulders to the head or cervical vertebrse. The mus-
cles of the neck, then, are the principal support of the
chest, and are directly interested in elevating the ribs
and shoulders during inspiration. Their action must be
very much increased when there exists " a difficulty of
breathing." But you know that when muscles are
much exercised they grow larger, and when kept un-
naturally at rest they lose their tone. Please to hold
this in mind for a few minutes.

474. You see that the ribs resemble hoops, all leaning
downward in front, the lower being much more oblique
in their position than the upper ones. As the back ends
of the ribs cannot rise, because they are closely articu-
late I with the spine, it is the fi-ont of the chest that

18*

214 STRUCTURE OF THE THORAX.

must be alternately lifted and depressed in breathing.
When the hoops rise, it is very plain that the sternum
must be thrust further from the spine, particularly at its
lower end, where, from the greater length and obliquity
ol the ribs, the increased size of the chest in inspiration
is greatest. Providence designed this portion of the
chest to be the largest in circumference, as you may
judge by a glance at the skeleton (fig. 46) ; but many
silly people think it would have been much better formed
had it been made the smallest.

475. Now, suppose you were to employ a tight liga-
ture or band to bind the ribs and sternum firmly to-
wards the spine, so that it should be difficult to breathe i
would you not expect the muscles of the breast to be
weakened by unnatural rest, and those of the neck
enormously enlarged by continual exercise ?

476. There is a very wide but thin cutaneous muscle
on each side of the neck, the model of that with which
a horse shakes flies from the neck by twitching the skin.
In man it is generally useless, few persons having the
command of its action. But when the breathing be-
comes very diflicult, this feeble muscle involuntarily
endeavours to assist in elevating the chest, useless as its
efforts must be — for it belongs more properly to the skin,
and all its attachments to the parts within it are merely
cellular, except at one spot where it has a fibrous con-
nexion with the side of the lower jaw. This muscle is
broadly attached to the skin of the breast at one ex-
tremity, and to that of the face, particularly about the
angle of the mouth, at the other. When called into
action, this muscle gives a careworn expression to the
cheek, and draws downward the angle of the mouth into
an attitude of grumness.

477. Now, oblige me by reviewing the last five para-
graphs, and then reply to a plain question. Why is it
that a physiologist, when he sees a remarkably slender
waist, accompanied by a neck distorted by large and
wire-drawn muscles, small and high shoulders, and a
sullen look in a face designed by Providence to be —
what I might have described ichen younger — why is it,

BONY STRUCTURE OF THE PELVIS. 215

I say, that he turns so sorrowfully away to muse upon
the gross misapplication of so much mechanical genius?

478. I have said that the chest and shoulders are
mainly supported and elevated by the muscles of the
neck. But these muscles, being chiefly attached to the
head, their action tends constantly to drag the head and
the cervical portion of the spine forward towards the
chest. It is therefore requisite that the head and spine
should be kept erect, or the principal motion of the ribs
in breathing will be very much limited. The manly
port in an erect attitude depends chiefly upon the tone
and action of the multitude of muscles of the back
which originate from all the spinous and transverse
processes of the vertebrae, running from one to another,
and binding them strongly to each other, or passing
on to be inserted into the back of the head. It follows
obviously from these facts, that if disease or art should
deprive the nmscles of the back of their proper exercise,
so as to enfeeble them, the due support of the head and
spine must be lost, the muscles of the neck can no
longer elevate or support the chest in a proper man-
ner, and respiration must be imperfectly performed.

479. When you recollect that perfect respiration is
necessary to perfect nutrition, that the muscles, like
other parts, depend for their functional power upon a
supply of pure blood, and that parts already weakened
must suflfer most from all causes of debility, you will at
once perceive how a weakness of the spine and a limi-
tation of the motion of the ribs, produced naturally or
by the follies of fashion, mutually and rapidly increase
each other until they termmate in ihe most terrible
deformity and the utter destruction of health and com-
fort. Even a habitual stoop, and the custom of leaning
over a desk in writing, are evidently primary causes of
such evils, and the reason why they so often produce
diseases of the lungs by limiting the exercise of their
functions is equally plain.

480. The pelvis, the basin, or lower portion of the bony
structure of the trunk, requires but a passing remark.
It is formed of four bones, each of which is divided into

21 fj OF THE SACRUM AXD COCCYX.

several portions in children. The first of these bones
M'hich I shall mention is the sacrum, seen at t, fig. 46.
It is composed of five imperfect or false vertebra?, which
are separate in childhood, but form a single piece in the
adult. This bone is articulated, at its upper extremity,
with the last lumbar vertebra. It represents an irregu-
lar inverted pyramid very much flattened on the anterior
and posterior sides, and strongly curved, presenting its
concavity forwards towards the cavity of the pelvis.
The spinal canal is continued from the vertebra?, along
the back of this bone, but near its lower extremity the
spinous processes are wanting, and the canal becomes a
groove. Four holes penetrate this bone, having small
posterior and large anterior orifices, for the passage of
some of the great nerves of feeling and voluntary mo-
tion coming oft' from the lower part of the spinal mar-
row. The sacrum is generally considered as a part of
the spine by anatomical w^riters.

481. The coccyx, or os coccygis, is a small bone ap-
pended to the point of the sacrum, and seems to complete
its curvature. It is altogether unimportant to us in the
course of our present studies, and it is sufl^cient to name
it, with the remark that it completes the spinal column,
and is composed of several very diminutive false verte-
bra? united together.

482. With the sacrum and coccyx, the two share or
haunch bones, called, very ridiculously, the ossa innomi-
naia or nameless bones by anatomists, complete the
pelvis. You see their general figure, which is too
irregular for description here, at s, fig. 46, and j, ;, fig.
47. In childhood they are each divided into three
bones, bearing distinct names, which it would only
perplex your memory to mention. On the outer sides of
these bones are two very deep cups of bone, lined with
cartilage, each designed for the reception of the large
round head of the corresponding femur, os femoris, or
thigh bone, which with the cup forms the hip-joint.

483. Let us now take a hasty glance at the bones of
the extremities. As it is not a part of my plan to enter
more fully into the description of the anatomical struc-

OF THE CLAVICLE AND SCAPULA. 217

ture of the human frame than is absolutely necessary for
the purpose of rendering our physiological remarks intel-
ligible, I shall not attempt to describe in words the
general form of the bones of the extremities. All the
knowledge requisite for our present purpose may be
obtained from a hasty notice of their number and a
few of their peculiarities. The figures of the skeleton
presented at pages 190 and 191, will convey a tolerable
idea of the dimensions and shape of each of these bones.

484. The upper part of the superior extremity, called
the shoulder, is formed upon two bones : the clavicle
or collar-bone, (fig. 46, A, fig. 47, e,) — which is united
with the sternum, as you have been already informed,
by means of a moveable joint at its inner extremity, —
is also articulated, at its outer extremity, with a large,
broad, triangular bone, called the shoulder-hlade or
scapula (fig. 47,/). This joint is also moveable. The
collar-bone acts like a lever. Although many strong
muscles arising from the head, back, loins, and breast
are inserted into the scapula, or into the arm, which is
suspended from it, and although all these muscles, when
in action, tend to draw the top of the arm and shoulder-
blade inwards towards the spine, the collar-bone pre-
vents them from accomplishing this purpose. All that
these muscles can effect is, to raise or draw down the
point of the shoulder, by tilting the clavicle, which is
then made to move like the spoke of a wheel around its
joint with the sternum, which may be regarded as the
hub of the wheel. The arm, being thus kept con-
tinually at a proper distance from the side, has a fair
chance of moving in all directions. It can strike a
blow upon an object placed behind the person, and the
hand is permitted to reach all parts of the back.

485. To convince yourself that this freedom of mo-
tion could not exist in the absence of a clavicle, you
may watch the motions of the domestic cat — an ex-
ceedingly active animal, but one in which a very slender
and flexible ligament supplies the place of the collar-
bone. These animals can clasp a mouse or any other

218 OF THE bllOULDER-JOIIVT.

object closely to their breast, and they can strike, most
powerfully, downwards or inwards; but they can do no
injury by throwing the back of the paw' forward ; and if
an unwelcome visiter should trouble them behind the eor,
they have no remedy but an awkward scratciiing with
the hinder claws. Such is the case with all quadrupeds
that seize their prey by leaping, and with others which
require but little extent of motion with great strength in
their anterior extremities.

486. On the back of the scapula, a little above the
middle of the bone, you may see a strong, elevated
ridge of bone, called the spine of the scapula, which
rises higher and higher as it approaches the shoulder-
joint (484), and terminates in a broad beak, hanging
over that joint, and forming wdiat we commonly call
the point of the shoulder. This is the part of the bone
with which the outer end of the clavicle is articulated;
as has been already mentioned.

487. By glancing at/»fig. 47, you will observe that
the sharpest angle of the triangle formed by the scapula
is directed towards the shoulder-joint. It is placed
immediately under the broad beak of bone mentioned
in the last paragraph ; and it terminates in a process or
projection of bone shaped like the cup of the common
plaything called a cup and ball. The cavity of this
process, which is very shallow, is covered with carti-
lage. It is exactly fitted to the head, or round projec-
tion seen at the upper part of the humerus or bone of
the arm (fig. 46, /, fig. 47, g), which is also covered
with cartilage ; and these two parts — the cup and ball
— form the shoulder-joint.

488. The shallowness of this joint permits the bone of
the arm to roll freely in the socket through more than
the third of a circle upon its axis, and to point in all
directions throughout about the half of a sphere, with-
out calling for any motion in the elbow^-joint. This is
one of the most important advantages which man
enjoys over the brute. But the same cause renders the
arm very liable to dislocation, because the socket yields

OF THE RADIUS AND ULNA. 219

very little support to the ball ; and its security, there-
fore, depends almost exclusively upon the tonicity of
the muscles and the strength of the ligaments.

489. The lower extremity of the humerus is much
flattened before and behind, and extended laterally, so
as to form two condyles, which, taken together, look
not unlike a very short map wound upon its roller, the
ends of which — to continue the figure — project a little,
to furnish attachments for muscles, and set crosswise on
the end of the shaft, looking towards its front side.
Around the middle of the scroll there is an elevated
ridge, separating the two condyles from each other,
and both these prominences of bone are covered with
cartilage, being designed to assist in forming the elbow-
joint.

490. The forearm is constructed upon two bones, the
radius and the ulna; both of which contribute to the
formation of the elbow-joint. But the latter is much
more extensively connected with the humerus than the
former.

491. The ulna (fig. 46, /, fig. 47, i,) is thick and
strong above, and tapers off till it becomes very deli-
cate at the wrist. At the elbow it grasps the back
part of the inner condyle of the bone of the arm, in
much the same manner that a hand, with the fingers
half closed, would grasp a roll of paper. The part cor-
responding with the ends of the fingers has a deep
cavity formed for its accommodation, in the back
part of the lower end of the humerus, so that when the
forearm is fully extended, this projection of the ulna
comes into contact with the bone of the arm, and
checks further motion in that direction. On the con-
trary, the part corresponding to the heel of the hand at
the wrist, projects a little, forming a point which is
received into another shallower depression in front of
the shaft of the humerus, just above the condyles, when
the forearm is properly bent. This checks too great
flexion of the arm.

492. The radius (fig. 46, h, fig. 47, h,) is slender above,
and becomes thick and strong below, where it forms

220 OF THE WRIST AND HAND.

nearly all the upper half of the joint of the wrist. Its
upper extremity terminates in a thick ring of bone called
the head, laid flat across the shaft, and covered with
cartilage both on its edge and its upper side. The latter
surface is hollowed out a little like a cup, and fits on to
the outer condyle, thus contributing to form the beauti-
ful but complex hinge of the elbow-joint.

493. When the palm of the hand is directed forwards,
in what is called the supine position, \\\q radius and ulna
lie nearly parallel ; but when it is directed backwards,
or in the prone position, these bones are crossed upon
each other like the legs, when one limb is thrown over
the other as we sit on a chair. This twisting of the
bones results from the lower end of the radius following
all the motions of the hand, as it turns with it upon the
lower end of the ulna, as on a pivot. In order to per-
mit this motion, the edge of the ring or head of the
radius is received into a corresponding excavation in the
side of the upper end of the ulna, also lined with carti-
lage, and is there bound by a ligament that surrounds
and embraces it. The lower end of the ulna, which is
a Httle enlarged, so as to form a small head, is received
into a similar excavation in the corresponding part of
the radius; and thus the latter bone slides freely round
it, as the position of the hand is changed.

494. The lower and larger extremity of the radius is
slightly excavated and covered with cartilage, and part
of the narrow ^nd of the ulna is coated in a similar
manner, for the proper construction of the joint of the
wrist.

495. The wrist is composed of no less than eight
small bones, (fig. 46, m,) which it is unnecessary and
would be tedious to describe. They are united together
by numerous joints and many powerful ligaments, which
permit them to move upon each other to a certain ex-
tent, so as to contribute in a considerable degree to the
incalculably numerous and delicate changes of form that
render the human hand one of the greatest wonders of
creative power. They are all collected into the space
intervening between the wrist-joint and that part of the

OF THE WRIST AND HAND. 221

hand where the wristband of the shirt usually terminates.
Collected into one naass, called the carpus, they form, at
their upper extremity, a regular arch, so fitted to the ca-
vity formed by the ends of the two bones of the forearm
as to complete the joint of the wrist; allowing the hand
to be flexed or extended, or to rock from side to side as
far as the neighbouring ligaments permit.

496. At the lower extremity of the united bones of
the wrist the surface of the mass is very irregular, to
form strong joints, with five small, long bones, called
the metacarpal bones (fig. 46, n). These long bones
may be plainly felt as they lie buried in the substance of
the palm of the hand. The joints between the metacar-
pal bones of the fingers and the bones of the wrist enjoy
but a very slight extent of motion ; but the correspondent
joint of the metacarpal bone of the thumb is much more
free, permitting the ball of the thumb to roll forward, so
as to be opposed to the palm.. It is this that confers
upon us the power of grasping, and enables us to prac-
tise a thousand mechanic arts which quadrupeds would
never be able to acquire, even if they were endowed
with human reason.

497. With the lower extremities of the metacarpal
bones, and with each other, the long bones of the fingers
and thumb form regular joints, having a hinge-like mo-
tion. The fingers have three ranges of these long bones,
while the thumb has but two. The ranges are called
phalanges, and the bones the phalangeal hones. It is
unnecessary to describe their forms, which you can
examine upon your own person. The phalanges are
seen in fig. 46, o, p, r.

498. The whole number of bones above described as
appertaining to each of the superior extremities is thirty-
two ; of which two belong to the shoulder, one to the
arm, two to the forearm, and twenty-seven to the hand.
Besides these, we often find several small bones, not
directly connected with the skeleton, but buried in the
fibres of some of the principal tendons, as they pass over
the joints of the fingers or thumb. These are designed
to serve as pullies, and enable the muscles to act at a

222 OF THE FEMUR AND HIP-JOINT.

greater mechanical advantage. In some instances they
are coated with cartilages on the side next ihe corres-
ponding joint, to the ibrmation of which they then con-
tribute.

499. Let us now proceed to consider the bones of the
inferior extremities. These are so similar in their gene-
ral arrangement to those of the superior extremities —
the thigh answering to the arm, the leg to the forearm,
and the foot to the hand — that it will be sutBcient foi
our purpose to point out the principal points of difference

500. There are no bones in the lower extremity an
swering to the clavicle and the scapula. The manner
in which the hip-joint is formed has been partly described
already (482), and it only remains for me to mention
that the cup-like cavity of the joint is very deep, em-
bracing a considerable part of the ball or round head of
the femur or thigh bone. It is called the acetabulum, or
little vinegar cup, by anatomists. This arrangement
permits the lower extremity to move in all directions,
and to roll upon its axis, so as to point the toes inwards
or outwards ; but all these motions are much more
closely limited than they are in the superior extremity,
because the cup-like cavity of the shoulder joint is much
smaller and more shallow than the acetabulum.

501. The head of the thigh bone is not seated directly
on the shaft, like that of the arm, but is supported upon
the end of a long portion of bone shooting obliquely up-
wards from the inner side of the shaft, and called the
neck of the femur. You may see this arrangement very
clearly portrayed in fig. 46, u, in the left limb.

502. As we advance towards old age, the neck of the
femur gradually increases its angle with the shaft, until
it approaches the direction of a perpendicular to the
general course of the bone. When this change has
been effected, the neck is much more liable to fracture
from slight accidents, such as stepping suddenly from a
high curbstone or carelessly descending a stairway. If
you have been instructed in the first principles of the
science of mechanics, you will be able to comprehend
the reason of this fact ; and if not, you will perceive at

OF THE KNEE AND LEG. 223

once the importance of such knowledge to those who
would understand their own personal interests ; for all
branches of science are so intimately connected that a
knowledge of one of them throws light upon all the
others. A fracture of the neck of the thigh bone rarely
occurs before the age of forty years, and it is one of the
most serious accidents of advanced life.

503. Sometimes the changes attending advancing age
go further, and the neck of the thigh bone is absorbed.
The head of the femur then rests directly upon the shaft,
and the motions of the joint are very seriously limited.
This change is one of the causes that produce the stiff-
ness of motion in extreme old age, and contributes, to-
gether with the shortening of the neck (501), to the
diminution of stature observed at the same period of
existence.

504. The head and neck of the femur, like the lower
extremity of the same bone, and, indeed, all the extremi-
ties of all the long bones, are spongy or cellular in their
structure — a point which I must request you to bear in
especial remembrance.

505. The thigh bone tends obliquely inwards and
downwards from the hip to the knee-joint ; and near the
latter it is expanded, so as to produce tw^o very large
condyles, forming the upper half of the knee-joint.

506. The leg having two bones, (fig. 46, y, w, fig. 47,
71,0,) like the forearm, it is right to remark that only
one of these bones, called the tibia, (fig. 46, id, fig. 47, n,)
contributes to the formation of the knee-joint. It is very
thick at its upper end, but becomes narrower below.
The other bone of the leg, which is thin and delicate, is
called the fibula, (fig. 46, v, fig. 47, o.) Unlike its pro-
totype, the radius (492), its lower extremity assists in
forming the ankle-joint, but its upper end is articulated
with the tibia at a point entirely below the knee, and
enjoys exceedingly little motion.

507. The two condyles of the femur fit accurately
into two corresponding depressions in the head of the
tibia, and thus form the chief part of the knee-joint. But
there is a third bone interested in this structure, called

224 OF THE ANKLE AND FOOT.

the patella, which means a little shield. It is commonly
called the knee-pan. You see it represented in fig. 46,
in front of the knee-joint. The patella is not directly
connected with the skeleton, but lies buried in the ten-
don of the principal muscles which straighten the leg.
These muscles, by means of their tendon, are inserted
into its upper side ; the tendinoirs fibres penetrate its
substance ; and many of them, passing beyond it, are
inserted into the front part of the head of the tibia. The
patella, therefore, acts like a pully, to give a greater me-
chanical advantage to the action of the muscles. Its
inner surface is lined with cartilage, and contributes,
with the tibia and fibula, to form the joint.

508. Though the tonicity of the very large muscles
surrounding the knee-joint gives very considerable sup-
port to the bones of the leg, very strong ligaments are
also required to prevent injury from too sudden shocks,
to w^hich the lower extremities are continually subjected.
The perpendicular attitude of the leg and the obliquity
of the thigh produce such an efiect, that in all falls upon
the feet there is a disposition in the femur to tilt out-
wards ; and consequently the inner side of the joint is
much more liable to sprains than the outer. It is there-
fore provided with a very strong lateral ligament on
that side. In violent leaps, or other feats of agility, this
ligament is occasionally strained ; and such accidents
give rise to a most troublesome lameness, which some-
times proves incurable.

509. The ankle-joint has little power beyond the sim-
ple hinge-like motion, which allows the foot to be flexed
or extended. The other motions of the foot, complex
and beautiful as they are, result almost exclusively from
the joints connecting with each other seven spongy
bones, called the tarsal bones, (Fig. 46, x. Fig. 47, p,)

510. These tarsal bones, viewed as part of the frame
of the lower extremity, correspond with those of the
carpus or wrist (495) in their relative position; but they
are much larger and less numerous, for there are but
seven instead of eight of them. One of them is princi-
pally concerned in completing the ankle-joint, and an-

INELASTIC CHARACTER OF THE SKELETON. 225

other forms the heel. I might dwell for hours upon the
wonderful motions of the many joints of the tarsus, but
our subject and our plan will not warrant the indulgence.

511. The bones in the lower extremity answering to
the metacarpal bones of the hands are called the meta-
tarsal bones. These, with the phalanges of the toes, are
similar in number and general form to the correspond-
ing parts of the superior extremity.

512. As the bones corresponding to the scapula and
clavicle are wanting — as the number of bones of the
tarsus is one less than that of the carpus — and as the
patella is a bone peculiar to the knee-joint, the whole
number of osseous pieces in each inferior extremity is
thirty (498).

513. The skeleton, constructed as I have represented,
would fall to pieces at once, when placed in an erect
attitude, if the bones were not held together by strong
attachments. The ligaments contribute to prevent such
a catastrophe very essentially ; but as these organs are
long enough to permit all the necessary motions of the
joints, and do not contract like muscles, they can only
prevent the parts of the skeleton from separating widely
from each other, and cannot of themselves preserve the
upright and correct position of the frame. This duty
is performed by the muscles, which, passing from one
bone to another, and being always in a state of tonic
contraction while w^e are awake, effectually prevent any
very material bending of the trunk or limbs without the
permission of the will.

514. In falls from a considerable height, or when we
step suddenly down a stair or over a curbstone, the jar
would be felt very severely even by the head, if there
were no provision to deaden the force of the blow.
Take two or three marbles, such as are used by children
at play; range them in a row, so that they may touch
each other, and let a companion steady them in that
position by placing a finger over each of them ; then
place another in contact with the last of the series, but
do not confine it with the finger. Things being thus
prepared, if you roll another marble against the first of

19*

226 INELASTIC CHARACTER OF THE SKELETON.

the series, the last will fly off with nearly as much force
as your blow has impressed. This is a property of all
elastic bodies, which is commonly illustrated, in schools
that teach mechanics, by means of a number of ivory
balls suspended upon cords, as probably you have seen.
If you try the same experiment, after substituting a little
ball of hard dough or other inelastic matter for one of
the marbles held under the fingers, the last of the series
will hardly move at all. Now, ivory is the most per-
fectly elastic of all known substances;* and the more
solid parts of bone very closely resemble ivory. If, then,
all the pieces of the skeleton were composed of solid
bone, a jar received upon the feet would be transmitted
from one bone to another, until the last of the series,
which is the cranium, would feel almost the whole effect
of the blow ; and a fall upon the feet would then be
nearly as dangerous as a fall upon the head. Under
these circumstances, the thin bones of the cranium, being
ill adapted to sustain such violent concussions as are
often met with in the necessary accidents of life, would
yield readily to such forces, and most of us would be
killed by fractures of the skull and injury to the brain
before we had passed the period of infancy.

515. To prevent these evils, and for other equally
wise purposes, the bodies of the vertebrae (459), the
condyles of the occipital bone (428), the extremities of
all the long bones (389), and nearly all the thickness of
the bones of the tarsus (509), are of a loose and spongy
texture, so that these parts act like balls of dough inter-
posed between the marbles in our experiment (514), and
effectually prevent the transmission of violent jars from
one portion of the skeleton to another. In yielding this
security, they are aided very much by the elastic car-
tilages which form the surfaces of all the moveable joints.

516. An additional protection to the head results from
the curved form of the spinal column (fig. 44), w'hich

* Elasticity is not measured by the distance to which you can bend a
body without preventing it from returning- to its original form, but by
the suddenness with which it regains its first position, when indented or
bent. A body may be both higiily elastic and very brittle, like glass.

OF MUSCULAR EQUIL1B1RIUM. 227

being composed of many moveable pieces, supported in
their erect position by the tonicity of numerous muscles,
acts like a double spring between the head and the pel-
vis, to break the force of falls : for the muscles yield a
little to sudden extension, and immediately recover them-
selves under the action of the v^^ill ; thus allowing the
spine to bend and return again, very gradually, to its
proper form.

517. A similar arrangement is noticed in the structure
of the chest (fig. 49),forthe protection of the all-import-
ant organs contained in the cavity of that part of the
body.

518. The ribs (c, c, c), though literally long bones,
have no medullary cavity (390), but are composed of a
net-work of osseous fibres or cells in the interior, wdth a
very thin covering of not very solid bone. The sternum
(a) is of a similar structure. The cartilages of the ribs
which connect the anterior extremities of those bones
with the sternum, and which are seen, unmarked by any
letter, (between c and a,) are very elastic. If a blow
be struck upon the breast bone, part of its force is lost
in compressing the soft texture of the sternum ; another
part in the bending of the cartilages. If the blow be
very severe, the bony portions of the ribs act like dull
springs ; so that the force must be very great before it
can seriously injure the organs within the cavity.

CHAPTER XL

OF MUSCULAR STASIS OR EQUILIBRIUM.

519. As the proper position of the various parts of
the skeleton, ana, consequently, the attitude of the figure
of an individual, depends upon the proper balance of
action between the difl^erent muscles, it follows that any
thing which disturbs that balance must modify the atti-

228 OF MUSCULAR EQUILIBRIUM.

tude. ]f the cause which produces this modification be
permanent, the figure will be inevitably changed.

520. But you have been told that when a part is exer-
cised regularly and within certain limits, it increases in
size and strength. You have also been informed that
when a part is kept in idleness its nutrition is diminished,
and it becomes weaker, or loses its power altogether.

521. Any thing that improperly exercises or renders
idle a part of the frame, must destroy the proper balance
of action between that and other parts, and a certain
degree of deformity must necessarily result.

522. Now, apply these principles to the management
of the muscular system. We commonly use the right
arm most frequently ; hence it is generall}' larger and
stronger than the left, which is a deformity. But we
are more frequently called upon to apply force in exer-
tion upon things placed in front of the body than upon
those placed behind it; and we more frequently draw
things towards us than we thrust them from us. Now,
when we draw a thing towards us, we generally support
the weight of the body on the right leg, or keep it in
reserve to [rev^ent falling backward if our hold should
slip. In applying to the ground the force required to
give effect to the pull, the left foot is chiefly used. Try
this upon a rope, and you will perceive what 1 mean.
For this reason our left is generally stronger than our
right leg. — Another deformity. As the right arm and
shoulder are stronger than their fellows, we are naturally
inclined to use them in heavy pushing, and our principal
force is then naturally applied by means of the left leg.
This increases the deformity.

523. Boxing for boys, and battledoor for girls, are
well adapted to the correction, in part, of the error of form
that has just been described ; for they call the right leg
into unusual exertion, and thus promote its develope-
ment.

524. Persons who are left-handed naturally, or become
so by habit, undergo changes of figure exactly the re-
verse of those just pointed out. Thus, you perceive that
by unduly strengthening any particular set of muscles

OF MUSCULAR EQUILIBRIUM. 229

connected with the skeleton, we necessarily produce
more or less deformity, and a long series of alterations
often follows, until the whole appearance of the person
may be modified. This principle explains the peculiar
marks by which we can often tell at a glance to what
trade or profession an individual has been educated.

525. But the loss of power in any set of muscles by
inactivity or disease, is productive of equally remarkable
changes which are effected on the same principle, and
can often be predicted by an accomplished surgeon who
possesses physiological tact. For instance : if a child be
labouring under the deformity called club-foot, and the
affection be confined to the right limb, he cannot readily
support his person on the right foot, nor can he use the
left for the proper eftbrts in applying forces by means of
his right arm. The right lower extremity being thus
rendered in great degree useless, all the powerful exer-
cises that the unfortunate individual is capable of taKing
are performed on the left side of the body ; and conse-
quently, the whole of the right side of the person, together
with the bones themselves, soon loses its proper tone,
and finally becomes diminished in size for want of the
proper stimulus to nutrition. Such is the actual con-
dition of most persons in whom we notice the deformity
just mentioned.

526. But the evil stops not here. For want of proper
support on the right, the body rests on the left foot, and
of course the pelvis is bent or tilted downwards on the
former side. But this throws the whole upper part of
the figure so far to the right that the individual would
inevitably fall over if the spinal bones of the lumbar
region did not curve themselves so as to bring the upper
part of the body into an erect position. Thus begins a
curvature of the spine. But if the shoulders be carried
far to the left in order to balance the weight of the right
limb, the neck must take an opposite curvature to restore
the perpendicular position of the head. Thus the spine
is bent, laterally^ into the form of a letter S. Even the
dorsal portion of the spine (458) partakes of these

230 OF MUSCULAR EQUILIBRIUM.

changes. But the dorsal vertebree cannot be bent late-
rally to any considerable extent without changing the
relative positions of the ribs : they will be thrust nearer
together on one side, and unnaturally separated on the
other. The form of the chest is thus essentially altered,
and the functions of its contents embarrassed.

527. These false attitudes being frequently and neces-
sarily assumed^ the bones, ligaments and muscles become
adapted to their new relations. Those muscles which
are relaxed contract by their tonicity, and after a time
become really shorter, in consequence of a modification
of their nutrition ; while those which are extended be-
yond the proper point are exhausted, lose their tone, and
become attenuated, like an overwrought operative. All
the energy of the will can not then enable the individual
to restore the spine to its correct position, even for a
single moment. It remains displaced, like a bone that
has been long dislocated, and for the same reasons.

528. I might follow the train of unfortunate circum-
stances portrayed in the few last paragraphs much fur-
ther, but it is sufficient for my present purpose to explain
how vast are the evils which may follow so simple an
accident as the partial loss of the use of one foot in
childhood. Now, although these changes are rarely
carried very far in most cases of club-foot, yet their
presence, to a certain extent, is traceable in every case.
The side affected is always wasted, and the spine is
always more or less serpentine. You will immediately
infer, from the foregoing details, that even slight de-
rangements of the balance of muscular action, or, as it
may be properly termed, muscular stasis, are productive
of danger to health as well as strength, and must ulti-
mately overthrow our comforts and shorten our lives.
Let us apply this principle to the solution of some of our
ordinary habits and their consequences.

529. Until recently, all our schools were furnished
with stools divested of backs, for the use of the children.
It was thought that this promoted the formiation of a
good figure ! " Sit up straight and hold your shoulders
back" has been the universal order ; and the endeavour

OF MUSCULAR EQUILIBRIUM. 231

to support such an attitude has been continued under
magisterial jurisdiction for many hours in each day.
Now, no muscle can endure very long continued exer-
tion without intervals of rest; as I have remarked in a
former chapter. Of course, then, after a few minutes,
the child, endeavouring to sit erect on one of these in-
struments of torture, finds the muscles on the back of
the spine exhausted. They yield, and he stoops, until
the ligaments of the vertebra3 are put upon the stretch
so as to relieve the muscles. The body then forms an
arc, or bow, with the concavity forward. This embar-
rasses his breathing, and a severe oppression and a pro-
pensity to sigh soon shew the evils likely to result from
such a false position. But even the temporary relief
obtained from this yielding of the spine is denied, in
most instances, by the Vv'atchful oversight of the precep-
tor. " Sit up straight or you will spoil your figure. Miss
A — !" "Hold up your head and open your chest, or
you will ruin your health before you finish your studies,
Master B — !" Such are the orders, and the sufierer
endeavours to comply. What is the consequence? The
muscles of the back of the spine being utterly incapable
of keeping the column erect for more than a very few
minutes at a time, the student relieves himself by resting
first upon one hip, then on the other.

530. Now, as far as the spine is concerned, a person
sitting nearly erect upon one hip, is in exactly the con-
dition of the child who has a club-foot on the opposite
lower extremity. The pelvis and the vertebrae are twist-
ed in exactly the same manner (526). The muscles of
the spine on one side of the column are nearly at rest,
while those of the other side are put to unusual exertion.
If the weight of the body be regularly and frequently
thrown, first upon one hip and then on the other, an im-
perfect amount of rest is obtained ; and although the
respiration is not entirely free, and any liability to dis-
ease of the lungs already existing is increased, there is
little danger of serious deformity from this habit.

531. But the nature of the school studies does not
permit the pupil to repose alternately and equally upon

232 OF MUSCULAR EQUILIBRIUM.

each hip. The right hand is usually employed with the
book or the pen, and then the pupil invariably rests upon
the left hip. The consequences of such a habit are evi-
dently such as would follow club-foot upon the right side,
except that the right arm being chiefly exercised, while
the left arm is scarcely employed, the former is increased
in size and the latter enfeebled. The curvature of the
spine takes place in both cases alike.

532. But during writing lessons, as ordinarily prac-
tised, the student always rests his left arm upon the
desk ; and he naturally assumes the same position in
reading, when permitted to do so. Let us examine the
consequences of this position. The left shoulder is thrust
upwards, and the muscles which draw it downwards
are called into active exertion to support the weight of
the body, while those which elevate it, or, in other
words, those passing from the head and the vertebra of
the neck to the clavicle and scapula are relaxed, and
kept in an unnatural state of rest. The former are, there-
fore, unduly increased in strength, while the latter are
proportionally enfeebled.

533. The moment ihat a student who has long per-
severed in the bad habit just described attempts to sit
erect, or to rise from the desk, the left shoulder falls too
low for want of support. This defect explains the rea-
son why the dress is so apt to slide from the left shoul-
der in a majority of carefully educated females; and it
adds to and materially accelerates the progress of the
deformities pointed out in the last few paragraphs. But
our space will not allow me to dilate any further upon
this most important subject; and it would require a far
more thorough knowledge of anatomy than belongs to
an elementary education, to enable you fully to com-
prehend its details.

534. In order to avoid the vices of figure just pointed
out. it is necessary that the seats for pupils in schools
should be provided with backs, and that the students
should be permitted to use them. In writing, if the les-
sons be long continued without relaxation, the pupil
should be furnished with a desk nearly or quite horizon-

OF MUSCULAR EQUILIBRIUM. 233

tal, and should sit with the right side to the desk. The
paper should be placed in advance of the person ; the
body should be reclined a little backward, and the at-
tempt to lean over the paper ought to be immediately
checked. Long continued standing in classes should be
prohibited, and the student ought to be allowed to stand
at ease on each foot alternately. The drilling of young
children, like troops in line, for hours together, is ex-
tremely injurious, and confinement for a long time to a
given attitude as a punishment, is a proof of profound
ignorance of the laws of life.

535. An habitual stoop is chiefly the result of either
the undue strength of the muscles on the front of the
spine, which bend the column, or the undue weakness
of those of the back of the spine, which should hold it
erect. The rational modes of cure are those which tend
to strengthen the latter muscles by moderate exercise,
without fatigue ; for fatigue always weakens a part in-
stead of strengthening it.

536. Now nothing is more common than the attempt
to cure a stoop by Minerva braces, or bands designed to
draw the shoulders backward, and nothing is more likely
to occasion or increase a stoop. These braces support
the shoulders in the required position, as long as they
are kept in action; and, consequently, the muscles which
should effect this support, and which are already enfee-
bled, are relieved from all exertion. Under these cir-
cumstances they grow continually weaker, and the
moment the brace is removed the stoop reappears more
remarkably than before.

537. The proper mode of curing a stoop is to apply
forces occasionally, and for a reasonable time, calcu-
lated to draw the shoulders forward. This proceeding
obliges the muscles passing from the spine to the scapula
or shoulder-blade to exert themselves in resisting these
forces, and consequently they increase in strength ; so
that, when the forces are removed, they draw the shoul-
ders backward. To convince yourself of this fact, you
have only to compare the figure of a servant accustom-
ed to carrying a heavy tray with that of a soldier of the

234 OF MUSCULAR EQUILIBRIUM.

ranks, whose profession obliges him to attend drill and
nnarch under the weight of a knapsack. The moment
the former deposits the tray he becomes remarkably
erect, and his shoulders are firmly braced : the instant
the latter casts off his knapsack, he stoops and becomes
round-shouldered.

538. I will give you but one more illustration of the
deformity produced by undue exercise of particular
muscles, leaving you to apply the principles already
explained to the practical business of life, as your age
advances, and as the extent of your reading on anato-
mical subjects increases.

539. When you study optics, you will learn that the
human eye is so constructed that it must vary its shape
continually, according to the distance of the object upon
which the attention is directed ; for the eye, like a mag-
nifying glass, has its focus. Now you know that when
a magnifying glass is intended to have great power, it
is made very convex. When it is very convex you must
place an object very near the lens, in order to see it dis-
tinctly ; and the distance at which the object should be
held in order to be seen is inversely proportionate to the
convexity of the lens ; — it is called the focal distance.

540. Now, when we look at a distant object our eyes
require to be made less convex, and when the object is
more near, the}^ must become more convex in order that
we may see plainly. The power of effecting these
changes resides in the straight muscles of the eye (Fig.
27, a, b, c, d, p. 93). These muscles arise from the back
part of the orbit of the eye, and running forward so as
to embrace the eyeball above, below, and on each side,
are inserted by means of broad tendons into the outer
coat of the eye near the edge of the clear part, called
the cornea, through which we receive the light. These
muscles are of the mixed class, (138) being partly under
the control of the will, and partly involuntary. When
we are called upon to look at a near object, their toni-
city is increased without our consciousness ; they con-
tract, and by pressing firmly upon the eyeball, make the
front of the eye more convex and prominent. This ,is

OF MUSCULAR EQUILIBRIUM. 235

one reason why the eyes ache so severely when we
gaze for a long time at minute articles held very close
to our faces. On the contrary, when we look upon very
distant objects, the muscles lose their tone, become re-
laxed, and the eyeball expands by its elasticity ; thus
rendering the cornea flatter and less prominent.

541. The necessity for using spectacles with convex
glasses in old age results chiefly from a flattening of the
front of the eye, owing to a loss of tone in the muscles ;
and short-sightedness or nearness of sight in the young
is generally the result of bad habits at school in very
early life, though it frequently occurs naturally from
original defects either in the tone of the muscles or the
form of the ball. If a child be employed many hours in
the day in reading and writing at the desk, or studying
in a small room — if he be deprived of the opportunity
of recreation where he can gaze at distant objects, the
constant exercise of the straight muscles of the eye in
lessening the focal distance soon gives them undue
strength, and they become incapable of relaxing suffi-
ciently to allow the patient to see any thing distinctly
that is placed beyond the distance of a few feet. Short-
ness of sight, when the result of habit, may be cured
by proper muscular exercise, if attended to at an early
age; but as it is the involuntary power of the muscles
that produces the deformity, it is the involuntary power
that must be exercised to remove it. And how is this
to be accomplished? Simply by making efforts to see
distinctly objects placed beyond the acquired focal dis-
tance of vision. This will exercise and strengthen the
peculiar involuntary function of the nerves supplying
these muscles, by which the latter are left free to relax
themselves, and their tonicity, being less frequently
called into exertion, they become weaker and therefore
more useful.

542. Most persons who are very short or near-sighted
will be found affected with strabismus or squinting, and
I will explain the reason. We always look at an object
with both our eyes on all ordinary occasions ; and, con-
sequently, the lines of the direction of the sight in the

236 OF MUSCULAR EQUILIBRIUM.

two eyes are not parallel to each other. Both lines tend
to a point at the object. Now, in looking at a fixed
star, the sun, or any other very distant object, the obli-
quity of the eye is too slight to be perceived : but take
a bright button, or any other snaall body, and bring it
gradually nearer to the nose of one of your playmates.
Tell him to look at it, and you will perceive that the
nearer it approaches, the Qiore he will squint. He
cannot possibly look at any thing with both eyes with-
out squinting sufficiently to bring them both to bear
upon it. The obliquity of the lines of sight is of course
the result of an involuntary contraction of the internal
straight or rectus muscles of the eye (fig. 27, b) ; and if
the individual be in the constant habit of gazing at his
books, his papers, or the things immediately around
him, these muscles are very apt to become even
stronger proportionally than the other recti muscles.
The habit of squinting is then established, and unless
treated very early, cannot be relieved by any kind of
exercise. Fortunately, it has been recently discovered
that this deformity, so extremely disagreeable when
very considerable, may be readily cured by a surgical
operation that is neither very painful nor dangerous. It
consists in cutting a passage about half an inch deep
from the front of the eye into the orbit, between the ball
and the nose, then taking up the internal rectus muscle
on a silver hook, and cutting it off with sharp scissors.
The other muscles are capable of effecting all the ne-
cessary motions of the eye, by the aid of the oblique
muscles, one of which you have seen at e, fig. 27, and
the deformity is immediately much diminished, or en-
tirely removed.

543. Squinting is not generally the result of bad
habits. It is more frequently a mark of a faulty con-
struction of some part of the nervous system, frequently
within the brain ; and it oftens proves hereditary. But
these circumstances do not necessarily prevent the
operation above mentioned from curing the mechanical
diflSculty in the motion of the eye. Again; temporary
squinting is occasionally an important symptom of func-

OF MUSCULAR EQUILIBRIUM. 237

tional disorder in the brain, and can only be success-
fully treated by the cure of the disease on which that
disorder depends — a disease that may be seated origi-
nally in any part of the body, while the brain is merely
affected by sympathy with that part, through the media-
tion of the nerves.

544. A man who squints, sees distinctly with one
eye only — namely, that which is directed pro'perly to
the object of his attention. The other receives and
conveys a very obscure image. He cannot judge well
of distances ; and as the obliquity of vision is rarely
equal on both sides, he soon becomes accustomed to the
exclusive employment of the better eye alone. The
other then gradually loses its powers for want of use,
and often becomes much smaller by a diminution of its
nutrition ; for, as you have been led to conclude from
former remarks, little care is taken in preserving the
existence of organs that are no longer of use. The
heart, the blood-vessels, the nerves, and the absorbents
have enough to do without supplying food to agents that
will not work. If they do not let them absolutely starve^
it is only because there still may be some hope of ulti-
mate improvement. Even those that cannot ivork share
the same fate, and in this respect the operations of the
vital functions seem to have set a bad example to
society, which, I am sorry to say, is but too closely
followed by those who govern our public charities.
The operation already described leads to the speedy
removal of the evils mentioned in this paragraph, by
bringing the bad eye into action, improving its func-
tion, and inducing its developement.

545. Unequal action of the recti muscles of the two
eyes often brings about a difference of the focal dis-
tances : one becomes nearer sighted than the other,
and, as they do not agree, the habit of using only one
eye at a time is established from this cause. If the
patient uses glasses, he then requires them to be of dif-
ferent powers in order to see distinctly. This is unfor-
tunate, though it might be remedied in early youth by a
proper course ctf acyninastics of the eye. 1 might write

20*

238 OF MUSCULAR EQUILIBRIUM.

a volume on this novel subject to advantage, but it
would be vi^rong to do so in an elementary work. You
have the general principles laid down in the beginning
of this chapter, and if you reason logically in applying
them to actual circumstances, you will draw conclu-
sions as accurate as any I could give you, and much
more accurate, I trust, than most that you will find in
books. There is no branch of human science as yet so
perfected that a logical reasoner with moderate powers
and tolerable industry may not contribute essentially to
its perfection.

546. It is now time to give you a very few hints as
to the application of the same principles to the action
of the involuntary muscles. These belong, as you will
recollect, to those parts of the frame which perform the
functions of organic hfe ; and they are chiefly found
about the digestive apparatus. For the most part, their
fibres are arranged in the form of a coat or layer around
hollow organs, to enable them to press upon, to move,
or to expel their contents; and the manner of their
arrangement has been already described in the chapier
on the surfaces of the body. The tonicity of the fibres
of these muscles is so great that, when the cavities of
the organs which they envelope are empty, they gene-
rally contract so as to close those cavities ; but when
any thing is admitted in the cavities, the fibres are put
upon the stretch, or, in other words, they are exercised.
But I shall be better understood by making reference to
a particular case.

547. Fig. 50, represents the human stomach covered
with serous membrane, as will be described hereafter.
The end of the oesophagus is seen at a ; at c you observe
the upper extremity of the stomach where the food enters;
and at b, the lower extremity, from which it passes into
the intestines after it has been prepared by digestion. The
whole stom.ach is enveloped in a coat of muscular fibres
running round it in various directions, as has been already
mentioned, — (368,373). Now, at b there are a number
of circular fibres embracing the outlet, which are much
stronger than those found about other parts of the sto

OF MUSCULAR EQUILIBRIUM.

239

mach. They close the stomach entirely at this point,
except when they are relaxed to permit the chyme to
pass. This outlet of the stomach is called the fylo-
rus, and it is seen very distinctly in Fig. 54, at c, the
stomach being laid open in that figure.

Fig, 50.

548. When food is taken into the stomach, the pylorus
immediately contracts ; for undigested food is a strong
stimulus to the muscular fibres of that part ; but the other
fibres allow themselves to be stretched, so as to enlarge
the cavity. These latter then press gently upon the food,
and as the mucous coat of the stomach gradually dis-
solves the food into chyme, they move it from place to
place by a kind of serpentine, motion, so as to bring one
portion of undigested matter after another within the
range of action of the mucous coat, in order to be di-
gested. When any portion of chyme approaches the py-
lorus, it soothes the fibres and they relax, so as to permit
the prepared matter to pass through under the gentle
pressure produced by the tonicity of the stomach in ge-
neral; but the moment undigested food presents itself

240 OF MUSCULAR EQUILIBRIUM.

there the pylorus is firmly closed, and the food is com-
pelled to return by the serpentine motion until it is com-
pletely dissolved. Thus the fibres of the pylorus and
those of the rest of the stomach antagonise each other.

549. There are many other hollow organs in the body,
such as the gall-duct, for instance, which are provided
with muscular fibres at their outlet, arranged in the same
manner and exercising functions similar to those of the
pylorus. Such muscles, (for they «ire sufficiently distinct
from the neighbouring fibres to be regarded as separate
organs,) are termed sphincters.

550. When a hollow muscular cavity like the stomach
is frequently over-distended, the fibres of the walls of
the organ are over-exerted, and consequently, their tone
is lessened. TJiey may even he 'paralysed, but then death
soon closes the scene. Now, when they are thus ex-
hausted they cannot properly perform their functions.
In the case of the stomach, the food is not digested in
proper time, and the sphincter being constantly stimu-
lated by the presence of crude matter, also becomes ex-
hausted by over action, and ceases to exercise its pro-
per guardianship ; ill-digested particles then find their
way into the intestines with the chyme, and produce
irritation and disease. Need I say any thing further in
explanation of this cause of dyspepsia from excessive
eating or drinking? Some of the worst cases of dys-
pepsia are occasioned by a habit of drinking immoderate
quantities of cold water in childhood, when there is no
fever or other unusual cause of thirst to require it. Mo-
deration in all things is necessary to health.

551. The effects of food or drink of a character too
stimulating, do not difler very essentially from those of
milder articles taken in excessive quantities; but in this
case it is the nerves that are exercised too much, and
the muscular fibres lose their tone from the weakening
of the nervous influence. The same result may follow
a blow upon the back which jars the spinal marrow.
What think you then of the wisdom of an empiric, who
advertises some single remedy for dyspepsia, regardless

OF THE GREAT CAVITIES. 241

of the thousand causes of such affections, — of whicTi
causes I have named but three ?

552. With these remarks I quit the subject of muscu-
lar stasis or the balance of muscular action, having en-
deavoured to give you those general ideas which will
render your future reading and reflection on such mat-
ters easier and more profitable.

CHAPTER XII.

OF THE GREAT CAVITIES OF THE BODY.

553. As the walls of the great cavity of the head,
containing the brain, are entirely composed of bone,
their outline and the general form of the cavity have
been described in the chapter on the osseous system,
(chap. X.) But the thorax or chest, and the abdomen
with its appendage, the pelvis, are but partially surround-
ed by bone, as you have been informed in the same
chapter. I now wish to give you an idea of the manner
in which the walls of their cavities are completed.

554. The spaces between the ribs, (fig. 49, c, c, c,)
are occupied by muscular fibres arranged in two sets,
so as to form two muscles. One set run obliquely
downward from the lower edge of one rib to the upper
edge of that next below. The other set pass obliquely-
upward from the upper edge of one rib to the lower
edge of that next above. Thus the walls of the thorax
in the intervals of each pair of ribs are completed by
two thin layers of flesh. These are called the intercostal
muscles, and it is their function to draw the ribs nearer
together and lessen the intercostal spaces. Th^v belong
to the class of the mixed muscles, bei:^' ^ b ■'-►^J^d
by the will and partly involuntary.

555. A great many powerful and broad muscles
originate from the spine and the back of the occipital
bone, and cover the back of the chest, running to be

242 OF THE GREAT CAVITIES.

inserted into the scapula or the bone of the arm. They
draw the arm or the shoulder backwards when called
into action, and they very greatly increase the thickness
of the fleshy walls of the thorax. A part of one of the
largest of these muscles supports the scapula, and, by
that means, the whole upper extremity ; though it is
assisted in this duty by many others passing down from
the back of the head or the spinous processes of the
cervical vertebrae to the scapula, the clavicle, the
sternum, and the uppermost ribs.

556. On the front of the chest, the fleshy walls are
also strengthened in a similar manner, chiefly by three
large muscles originating from the ribs or their carti-
lages and the sternum, and passing, two to the scapula
and one to the bone of the arm. These muscles draw
the arm or the shoulder forwards. There are also a
great many other muscles connected with the structure
of the chest, but I do not mention them because I am
not writing upon anatomy. Enough has been said for
our present purpose.

557. You now understand how the sides of the chest,
seen at fig. 49, are completed, but you perceive that it
is still open at the top and bottom. Between the upper-
most dorsal vertebra, h, and the two uppermost ribs,
c, c, there is a small round opening corresponding with
the base of the neck, through which you might readily
pass your arm into the cavit}^ within the ribs. This
space is filled up by the muscles of the neck originating
from the clavicle, the sternum, the two uppermost pairs
of ribs, the transverse processes of the spine, &c. (555),
by the gullet or oesophagus which conveys the food to
the stomach, the trachea or air-passage to the lungs
(250), and the great arteries, veins, nerves, &c. pass
ing to and from the head, combined with the cellular
tissue and fat binding these various parts together.

558. But at the lower end of the thorax, correspond-
ing with the outline of the false ribs (472)* and the ensi-
form cartilage, you see the chest widely open towards
what was described to be the abdomen in the com-

* The false ribs are those whose cartilages do not reach the sternum.

CAVITY OF THE THORAX.

243

mencement of the last chapter (324). And how is this
opening closed, so as to make the chest a separate
cavity from the abdomen?

559. In fig. 51 you

Fig. 51.

are presented with a
front view of the trunk
of the body laid open
so as to expose the
cavity of the chest by
the removal of the
sternum and the carti-
lages of the true ribs.
The upper or first pair
of ribs being naturally
provided with little if
any cartilage, appears
as a pair of perfect
bones. The fleshy and
bony walls of the chest
are seen at 1, 1.

560. At the numbers
2, 2, you see a broad,
thin muscular organ
called the diaphragm.
It is this which com-
pletes the division be-
tween the thorax and
the abdomen. It arises,
by tendinous fibres, from
the front of the spine in
the lumbar region, and
by fleshy fibres from the cartilages and bones of the
false ribs as well as from the ensiform cartilage. The
middle of the diaphragm, where the figures are placed,
is composed of tendinous matter, and the whole consti-
tutes a broad, thin, complex muscle, forming a division
between the cavities of the chest and abdomen. It is
penetrated by the oesophagus on its way to the stomach,
by the aorta (264) conveying the blood towards the
lower extremities, and by the ascending vena cava

Section of the Great Cavities.

244 OF THE GREAT CAVITIES.

(263) and the thoracic duct (197) on their way towards
the heart.

561. The diaphragm may be readily compared to an
inverted basin, its bottom being turned upward into the
thorax while its edge corresponds with the outline of
the lower edges of the false ribs and the sternum. Its
cavity being directed towards the abdomen, it enlarges
that cavity very much at the expense of that of the
chest, which it contracts to an equal extent, as you see
in fig. 50.

562. Having now completed our view of the walls of
the thorax, it will be proper to say something of its
principal contents. The cavity of the chest is almost
exclusively occupied by the right and left lungs (249),
the heart, and great vessels (264). The heart is situated
between the two lungs, but extends much farther to the
left than the right, thus rendering the left lung smaller
than its fellow. The heart reposes upon the upper sur-
face of the diaphragm, with its point far to the left and
near the front of the breast, where we feel it beating,
between the ribs. Its auricles are directed towards the
right and backwards.

563. Now both the lungs and the heart are almost
constantly in motion, and would be embarrassed or
injured by friction against neighbouring parts were they
not protected by a peculiar arrangement. You have
read of the synovial membranes, which are designed to
protect the articular cartilages against friction (172),
and something resembling these are furnished to all
organs contained in the great cavities of the body.
They are termed serous membranes, and contain nothing
but a little seriiw., much like that highly fluid portion of
blood in which the red coagulated portion floats in the
bowl a few hours after bleeding, or that fluid which
fills the cells of the cellular tissue in common dropsy.

564. It is usually considered extremely difficult to
convey a clear idea of the arrangement of the serous
membranes by means of w^ords or drawings ; but I
must endeavour to do so by resorting to a very homely
comparison. Suppose a common pillow-case sewed up

SEROUS MEMBRANES OF THE THORAX. 245

into a sac, to represent a serous membrane, and your
clenched fist to be an organ requiring such a protec-
tion. Thrust your fist ihto one end of the sac, so as to
invert the latter, as we sometimes invert the finger of a
glove. Your hand is now in nearly the same condition
with an organ covered by its serious membrane. It is
not in the pillow-case, but is surrounded by it; and if
you rub the hand thus enclosed against any hard sub-
stance, you find it in great degree protected from the
friction by the sliding of the outer over the inner layer
of linen that covers it. But usually the layer of serous
membrane next the enclosed organ adheres firmly to its
surface, as the corresponding layer of the pillow-case
would adhere to your hand if it were covered with tar.
You have only to conceive then, that the pillow-case is
moistened within by a very little fluid, and you have a
tolerable picture of the arrangement under description.
Every organ has blood-vessels, nerves, &,c., and most
of them have ducts passing to and from them. Now
these never penetrate a serous membrane, and must find
their way to the organ through the opening by which
we suppose it thrust into the inverted sac ; and in our
little experiment, they may be represented by your arm,
as it passes in to join your fist within the sac.

56.5. Each lung has its distinct serous membrane,
called a pleura, which adheres to its surface, and then
envelopes it, as in a bag. The outer part of the pleura
adheres to the corresponding side of the cavity of the
chest, and to the upper surface of the diaphragm,
furnishing them with an extremely thin, transparent,
and beautifully smooth lining. At the middle of the
chest, the two pleurae come together, forming a kind of
double membranous partition passing from the sternum
to the spine, and dividing the cavity into two apart-
ments.

566. But the two layers of the partition are separated
widely from each other in front, to accommodate the
heart, which, being provided with its own peculiar
serous membrane, called the pericardium (see fig. 34,
page 127), occupies a third chamber in the thorax.
2i

246 OF THE GREAT CAVITIES.

The two layers are separated near the spine to accom-
modate the great blood-vessels and other important
parts.

567. The trachea having divided into the tvi^o
bronchise, one of these enters the substance of each
lung, attended by the necessary blood-vessels, nerves,
and lymphatics, and is then distributed in the manner
already described at page 123.

568. The lungs and heart fill up nearly the entire
cavity of the chest. The former, being in communica-
tion with the external air through the open canal of the
trachea and the mouth and nose, are kept always in
contact with the walls of the cavity by atmospheric
pressure, dilating and contracting as the ribs rise and
fall in breathing. If a wound should penetrate the cavity,
the air is admitted into the serous sac of the pleura, and
the lung on the injured side being equally pressed upon
by the atmosphere on the outside and the inside, imme-
diately becomes collapsed, arresting the breathing on
that side, and leaving a large empty space between its
surface and the ribs. Were it not for the partition
formed by the pleura across the middle of the chest,
both lungs would be collapsed ; and if the patient were
not immediately relieved by art, he would inevitably die
in a few minutes.

569. Before speaking of the abdomen, which must be
described presently in order to enable you to compre-
hend the mechanism of breathing, I will seize this oppor-
tunity to say a few words about an important appendage
to the trachea: — the organ of the voice, called the
larynx.

570. In Fig. 52 you are presented with a view of the
upper extremity of the trachea, at^l Above this you
see a superstructure, somewhat complex in its arrange-
ment, which occupies the throat, between the root of the
tongue and the middle of the neck. This forms part of
the tube through which the air is inhaled to the lungs,
and it is composed of six cartilages. The first of these,
which is marked e, is called the cricoid cartilage. It is
little more than an enlargement of the uppermost ring

ORGAN OF THE VOICE.

247

Fig. 52.

of the trachea, but it
is essentially changed
in shape, being much
broader at its poste-
rior part than it is in
front. It encircles the
tube completely. Seat-
ed upon this ring, like
a saddle placed on end,
with its seat present-
ing forward towards
the throat, is the thy-
roid cartilage, d, the
upper and angular
point of which forms
the projection vulgarly
termed Adam's apple.
The thyroid partially
embraces the cricoid
cartilage with what
may be compared to
the flaps of the saddle :
but you will better un-
derstand this arrange-
ment by referring to
Fig. 53, in which the
larynx is represented
as it would appear to

an eye looking down perpendicularly into the wind-pipe.
571. In figure 53, / represents the high posterior
part of the cricoid cartilage ; a, a, the thyroid cartilage,
partly embracing the former, and rising high above it ;
b, b, two horns or processes projecting back from the
sides or flaps of the thyroid ; d, the passage for the en-
trance of the air into the trachea, called the glottis ; and
e, e, two other small cartilages of the larynx, called the
arytenoid cartilages. These last are articulated by move-
able joints upon two little prominences on the back part
of the upper edge of the ring formed by the cricoid
cartilage. From the bases of the arytenoid cartilages,

248

OF THE GREAT CAVITIES.

Fig, 53.

tendinous chords are
stretched forward to
the front angle of the
thyroid just below the
notch, which you per-
ceive in the niiddle of
its upper edge. These
chords are seen shin-
ing through the mu-
cous membrane close
to the side of the glot-
tis, in Fig. 53. They
can be tightened or
relaxed by means of
a number of beauti-
fully delicate muscles, passing from one to another of
the cartilages of the larynx, and thus the pitch of the
voice is elevated or depressed. For these chords act
like those of a violin, and are made to vibrate by the
air in such a way as to produce the tones of speech and
song* This fact will explain to you the reason why the
compass of the voice can be so much increased by well
regulated training. The muscles of the larynx may be
enlarged and strengthened by exercise, like all other
muscles ; and thus the art of elocution, so far as the
voice and gesture are concerned, becomes a branch of
gymnastics.

572. The mucous membrane lining the trachea hnes
also the cricoid cartilage, then sweeps through the
glottis, covers the vocal chords, and sinks down for a
short distance between these chords and the flaps of the
thyroid cartilage, so as to form the two little pockets
marked c, c, Fig. 53. The membrane then lines the
inside of the thyroid, and, rising above its upper margin,
is continued into the pharynx and the mouth.

573. At a, Fig. 52, you see the body of a curious
bone called the hyoid hone, which gives attachment to
the root of the tongue. It has two long horns projecting
backwards, which correspond pretty nearly in their

ORGAN OF THE VOICE. 249

course with the appendage of the thyroid, but lie some
distance above that cartilage.

574. The mucous membrane, in its course to the
mouth, fills up the space between the edge of the bone
and that of the cartilage, as you perceive at c, Fig. 52.
When we *' get a drop the wrong way," it is received
into one or other of the pockets at c, Fig. 53, where it
causes much irritation, and is displaced with difficulty
by coughing. Thus, the larynx is in a manner suspended
upon the hyoid bone, and is compelled to follow all its
motions. The bone itself is suspended upon two long
flexible ligaments coming from the base of the cranium,
but all its other connexions with the skeleton are merely
muscular, and bind it chiefly to the lower jaw. It moves
with every motion of that most moveable of organs, the
tongue, and as constantly influences the position of the
larynx. This will explain one principal reason why
inflammations of the larynx are so fatal to orators, min-
isters, lawyers, and others who are compelled to speak
frequently and for hours together. The inflamed part
can scarcely know any rest in persons of these pro-
fessions.

575. In the act of swallowing, the food passes over
the top of the larynx on its way to the pharynx and
CESophagus ; and, were there no arrangement to prevent
such consequences, the exquisitely sensitive edges of the
glottis that guard the entrance to the lungs would be
liable to perpetual irritation. The sixth cartilage of the
larynx affords this necessary protection to these parts.
It is called the epiglottis. In form it resembles the leaf
of a tree, and is attached by its stem to the notch in the
middle of the upper edge of the thyroid cartilage.

576. The position of this leaf is nearly perpendicular,
and it stands up in the throat, just behind the root of the
tongue, with its back towards the mouth and its front
towards the glottis. You see the point of the epiglottis
just peeping above the body of the hyoid bone at 6,
Fig. 52. It may be seen during life, in some individuals,
when the base of the tongue is depressed by a spoon or
the finger. Now, when the food leaves the mouth, on

21*

250 OF THE GREAT CAVITIES.

its way to the cEsophagus, this leaf is shut down, Hke a
lid, over the glottis, and completely protects it from irri-
tation. Sometimes it acts irregularly, and then we very
readily " get a drop the wrong way."

577. Referring once more to Fig. 51, you observe
how very incomplete are the bony walls of the abdomen.
Bounded above by the hollow of the diaphragm, it has
the five lumbar vertebrae behind, and the bones of the
pelvis or basin (3, 3) below. Between the lower mar-
gins of the false ribs and the upper edges of the ossa
innominata (482) no bone is visible. The pelvis is sur-
rounded and inclosed by many muscles, which thus
complete the walls of the abdomen in that direction, and
it is by muscles and their tendons that the wide open
space represented in the figure between the edges of the
ribs and the pelvis is filled up. It is only necessary to
glance at four pairs of these organs in this volume.

578. Three pairs of very broad, thin muscles, are
connected with six or eight of the lowermost ribs above,
with the spine behind, and with the edge of the pelvis
below. These muscles coming from each side of the loins
meet, and are inserted into each other in front, in such a
manner as to embrace the sides and the anterior part
of the abdomen with three distinct layers of flesh and
tendon. The innermost pair is composed of fibres pass-
ing directly round the body, so that almost their only
action is to compress the contents of the cavity which
they surround. The fibres of the second pair run ob-
liquely upwards from the upper edge of the pelvis and
the lower part of the spine towards the middle line of
the abdomen, where they meet and mingle with their
fellows from opposite sides, and the upper portions of
these muscles are inserted into the cartilages of the
seven lowest ribs and the ensiform cartilage. Of course,
when they contract, they not only compress the abdo-
men, but draw down the ribs and sternum ; thus assisting
in the process of breathing. The fibres of the third or
outer pair run obliquely downwards from the eight lower-
most ribs, and from the highest part of the upper edge
of the pelvis, and intermingle, like those of the second

WALLS OF THE ABDOMEN. 251

pair, with their fellows from the opposite sides. These
muscles also assist in drawing down the ribs in breath-
ing.

579. The two last mentioned pairs form very broad
and thin tendons, instead of fleshy fibres, over the greater
part of the front of the abdomen, so as not to increase
unnecessarily the thickness of the walls of the cavity.
These tendons, by a peculiar arrangement, which it is
not necessary to describe, form two long, tendinous
sheaths, running from near the lower end of the sternum
down to the upper edge of the pelvis, one on each side
of the middle line of the abdomen. In these sheaths are
enclosed two long, thick and powerful muscles, which
connect the cartilages of the three lowest pairs of true
ribs with the front of the pelvis. They are designed to
bend the body forwards. These eight muscles, together
with many others about the spine and loins, complete
the fleshy portion of the walls of the abdomen.

580. It is now time to enumerate, with a few com
ments, some of the principal organs contained in the
abdomen. Its cavity is lined throughout by a thin serous
sac, like the pleura in the chest, but it is called the peri-
toneum. One side of this sac adheres firmly to the
fleshy walls of the abdomen, including the under surface
of the diaphragm, and the other is thrown over the front
of a large number of important organs called, collec-
tively, the abdominal viscera, all of which are thrust
against the back or the upper part of the peritoneum, so
as to invert it, as the lungs and heart do their proper
serous membranes (564), and thus they all furnish them-
selves with a partial or complete covering of serous
membrane, commonly called their peritoneal coat.

581. Some of these organs, such as the small intes-
tines, invert the sac so far that they become completely
hidden, as a child's marble may be in the indented
finger of a glove. In such cases the two sides or folds
of the reversed portion of the peritoneum come nearly
together behind the included organ, and, by adhering to
the walls of the abdomen at the spot where the organ is
supposed to be thrust in, they bind it to the sides of the

252 OF THE GREAT CAVITIES.

cavity, acting like a ligament, while they allow it to
swing or move freely within certain limits. But these
folds always leave space enough between them, filled
with loose cellular tissue, to accommodate the blood-
vessels, nerves, &c. belonging to the organs.

582 Others of these viscera, like the liver and part
of the great intestine, revert the peritoneum far enough
to cover the chief part of their surface with serous
membrane, but leave a portion of their substance in con-
tact with the fleshy walls, to which they are so closely
bound down that they enjoy very little motion.

583. Others again, like the spleen and pancreas, are
covered on their front side by the peritoneum, which is
only sHghtly indented by them. These organs are not
allowed to change their place at all under any circum-
stances.

584. But the most curious of these arrangements is
seen in some of those organs that vary much in size at
diflerent times, and yet require a certain degree of free-
dom of motion. The stomach is one of these, for it is
greatly enlarged by eating, and becomes very small
when empty. If such organs were bound down to the
sides of the abdomen by the peritoneum as firmly as
some that have been mentioned, the membrane would
be burst when the organs become distended. To meet
this difliculty, the inverted portions of the peritoneum
about the stomach and some other parts of the alimen-
tary canal are much more extensive than necessary for
the accommodation of these parts in their common con-
dition, and then hang down from their front edges like
aprons, placing them very much in the condition of a
very small body in the iuA^erted finger of a very large
glove, and leaving them free to dilate to almost any ex-
tent. In the figure at page 239 you see this arrange-
ment, where c represents the free duplicated part of the
peritoneum hanging from the great arch of the stomach.
In this figure all the front part of the peritoneal sac
which lines the walls of the abdomen is of course re-
moved, in order to display the stomach.*

* I am well aware of the extreme difficulty of givirjg a clear idea in

PERITONEUM AND ABDOMINAL VISCERA. 253

585. You will observe, if you have comprehended the
three or four last paragraphs, that when we cut into the
cavity of the peritoneum, from the front of the abdomen,
the viscera appear as if they were all contained in that
cavity, as in a sac ; but, in reality, they are behind it,
because the peritoneum, instead of enclosing them, is
merely thrown over them like a wet pillow case, with
its posterior side folded about them so as to embrace
each of them more or less completely. You will also
observe that the abdomen has but one serous chamber,
while the chest has three (565,566). Let us now describe
the position of some of the principal abdominal viscera.

586. The liver is the largest gland in the body. It
fills up very accurately all the cavity of the diaphragm
on the right side (see Fig. 51), and extends over on to
the left side to a point nearly half way between the point
of the ensiform cartilage and the edges of the false ribs.
Being very thick behind, it tapers to an edge in front ;
and being very bulky on the right side, it is also bevelled
off to an edge on the left: so that it is placed very
obliquely, and at least three-fourths of its substance lies
under the false ribs on the right side of the abdomen.
Its front margin corresponds very nearly with the out-
line of the cartilages of these ribs, and crosses to the
left about the point of the ensiform cartilage, terminating
nearly under the spot where the number 2 is seen on the
left side of the diaphragm.

587. As the left lung fills up the space seen between
the convexity of the diaphragm on the left and the cor-
responding ribs — as the point of the heart is found with
a portion of the right lung in the same relative position
on the right — and, as the liver fills up considerably
more than one half the great cavity of the basin of the
diaphragm (561), it follows that a small sword passed
horizontally through the body, between the uppermost

words of the arrangement of the serous membranes, and diagrams are
of scarcely any assistance in the attempt. Fortunately a thorough
knowledge of the subject is not very essential to the general student, and
I must leave it to the intelligent and well-informed preceptor to illustrate
it more perfectly by models or actual specimens, should he deem it of
sufficient importance to iiis class.

254 OF THE GREAT CAVITIES.

of the ribs, might penetrate the lungs, the heart, and
the liver ; nothing but the diaphragm being interposed
between these important organs. The sword, in this
case, would pass just above the stomach, which fills up
the chief part of the basin of the diaphragm on the right
side, being in contact wath the lower surface of the
liver, which is rather concave, and accommodates it
beautifully.

588. The liver is divided into several lobes. Into the
fissures between them, the blood-vessels and nerves
enter, and from one of them the gall-duct comes out.
You have been told that the liver is an organ appro-
priated to the secretion of bile. On its under, concave
surface, you find the gall-bladder, or sac, designed to
retain the bile until it is wanted in the progress of diges-
tion.

589. Just below the stomach, on the left side of the
spine, but within the cavity of the abdomen, we find a
curious organ called the spleen. In bulk, when in health,
it may be compared to the hand of a stout man, though
it is much thicker and not so long. It is not a gland,
for it has no secretory duct; but it is composed, in a
great degree, of blood-vessels. In the absence of all
certain knowledge of its functions, we have been in the
habit of considering it as a kind of receptacle for the
surplus blood called to the internal organs when they
are brought very actively into play, whether in health
or disease (274), and it certainly seems well calculated
for such a purpose. In attacks of disease attended with
great determination of blood towards the abdomen, the
spleen is known to become distended with blood ; and
when chills of intermittent fever have continued for a
long time, it is not unusual for it to become permanently
enlarged to a great extent, constituting what is called,
in vulgar phrase, an ague cake,

590. But the chief purpose of the existence of the
abdomen is in the accommodation of those organs which
are interested in the great process of digestion, and it is
time for me to describe the route of the alimentary canal
which fills by far the greatest portion of the cavity.

DIVISIONS OF THE ALIMENTARY OANaL. 255

591. The oesophagus (fig. 54, a), ahnost immediately
after passing through the diaphragm, expands itself into a
large cavity resembling, in some degree, a chemist's re-
tort. This is the stomach, and the extremity by which
the oesophagus enters it is called the cardiac extremity.
You have been already informed, that the epithelium or
cuticle terminates at this spot, and you see this termina-
tion clearly represented at h in the accompanying wood-
cut, where the comparatively smooth lining of the nar-
row canal gives place to the corrugated mucous mem-
brane of the stomach, which is well displayed in the
figure ; for the stomach is there drawn as if one half of
it were removed to show the interior. At the other ex-
tremity c, you observe the sphincter or pylorus, which
prevents the food from leaving this cavity until its nu-
tritive portions are converted into chyme. The figure
represents tlie parts thrown far from their natural posi-
tion, in order to enable you to distinguish the different
portions of the alimentary canal, which are so obscured
in their ordinary arrangement, that one part conceals an-
other from the view.

592. The stomach stretches itself, like a bridge, ob-
liquely across the spine just below the liver, so that its
cardiac extremity is placed somewhat to the left of
the vertebral column and its pyloric orifice is situated a
little lower down, and on the right side of the spine.

593. The pyloric extremity opens into a long, narrow
tube, called the s?naU intestine ; the first portion of which
d extends nearly in a horizontal line from right to left,
crossing the spine in its course, and bound firmly to the
posterior part of the walls of the abdomen by the peri-
toneum. From the circumstance that this portion of
intestine is about twelve fingers' breadth in length, it is
termed the duodenum. It is a most important part of
the digestive apparatus, for it is here that the biliary
and pancreatic fluids are mingled with the chyme, to
effect that more perfect assimilation w^hich prepares it
to be taken up by the lacteals. At h, you observe a
portion of the biliary duct with some of its branches
coming from the liver, where the bile is secreted. At i,

■H

256

OF THE GREAT CAVITIES.

you have the gall-bladder, which contains the bile till it
is wanted in the intestine ; and k represents the conn-
mencement of the duct which conveys it to the duode-
num. At I you see the duct of the pancreas, with some
of its branches, carrying a fluid similar to the saliva to
be emptied into the duodenum along with the bile.

Fig. 54.

DIVISIONS OF THE ALIMENTARY CANAL. 257

594. From the left extremity of the duodenum, the
ahmentary canal is continued in the form of a very
long, nari-ovv tube, commonly known by the name of the
small intestines, and arbitrarily divided into two por-
tions, distinguished by the special names with which I
do not think it necessary to charge your memory. The
small intestines are thrust so far within the duplicature
of the posterior side of the peritoneal serous sac that
they are entirely enveloped by it, and stand at a con-
siderable distance from the walls of the abdomen. They
have, consequently, so much freedom of motion that
they sometimes get entangled with each other, or with
other parts, giving rise to very dangerous accidents.

595. It is in the small intestines, chiefly, that the
chyle is separated from the chyme, and absorbed by
the lacteals ; and to facilitate this process, the mucous
membrane of this part of the canal is rendered a great
deal longer than the cellular and muscular coats ; so
that it is thrown into numerous circular folds, which, in
some places, hang over each other like the shingles on
a roof, giving ample space for the absorbents to act on
the food as it passes, and preventing the escape of any
nutritive particles.

596. After wandering about in the abdomen through a
long course, marked in the figure by the arrows, the small
intestines at length terminate in the great intestine at e.
The sides or walls of the small intestine here project in
a singular manner, into the cavity of the great intestine,
so as to hang somewhat loosely in two festoons, form-
ing a very curious valve, on the same principle with
those already noticed as belonging to the veins.

597. The small intestine, instead of opening directly
into the end of the great intestine, penetrates its side at
the distance of a few inches from its extremity, and the
part of the latter which projects beyond the orifice, is
called the ccecum. At/, you see a little appendage to
the coecum, of which the intention has never been dis-
covered. It is called the worm-hke appendage, or apen-
dicula vermiformis.

258 OF THE GREAT CAVITIES.

598. The ccecum is situated in tlie hollow of the right
OS innominatum (482), where it is bound firmly down
by the peritoneum. From this point, the great intestine,
taking the name of colon, runs upwards on the right side
of the spine until it reaches the posterior edge of the
liver. Throughout this part of its course it is firmly
bound down by the peritoneum, but it then springs in a
very wide arch horizontally over the front of the abdo-
men to the left side, passing along very near the ante-
rior edge of the liver, a little below the ensiform carti-
lage, and in front of the stomach when that organ is
empty, and returning nearly to the left side of the spine.
During this part of its course it enjoys considerable
latitude of motion. The disease called colic, generally
consists in a spasmodic affection of the muscular fibres
of this part of the colon. From the point last men-
tioned, the great intestine runs down on the left side of
the spine, bound down pretty firmly by the peritoneum,
until it comes near the upper margin of the pelvis,
where it winds itself into the form of the letter S, form-
ing what is called the sigmoid Jiexure of the colon, g. At
the extremity of this flexure, it descends in a nearly
straight line into the pelvis, and is called the rectum.

599. Having now completed all that it is necessary
to say as to the position of the abdominal viscera, it is
right that I should notice a remarkable peculiarity of
their circulation. The blood conveyed to these organs
by the arteries does not return immediately into the
veins of the general or nutritive circulation, like that o^
other parts of the body (264). On the contrary, tho
veins originating from the viscera, are all gradually col
lected into one great venous trunk, called the portal
vein or vena poricB. This vessel conveys the blood to
the liver, and there divides, like an artery, into a pecu-
liar set of capillaries. It is from these xesseh, fil/ednnth
venous blood alone, that the bile is secreted; and this is
the only instance in which a secretion is formed from the
veins. After the blood in the portal capillaries has per-
formed its office, it is received into another set of vessels,
called the hepatic veins, which carry it back into the

PECULIAR ABDOMINAL BLOOD-VESSELS. 259

vena cava, where it again enters on the route of the ge-
neral circulation.

600. One of the principal ingredients of the bile is
carbon; — the very innpurity of venous blood that is chiefly
discharged from the body by means of respiration.
Thus you see that the liver and the lungs are occupied
in performing, to a certain extent, the same oflice, and
this explains the reason why any disease of one of these
organs is so apt to produce disease of the other ; for the
healthy organ is then obliged to perform extra duty.

601. There is another peculiarity of the veins of the
portal system, as it is called, that is worthy of notice.
They are not provided, like other veins, with valves.

602. The whole amount of blood contained in the
blood-vessels of the abdomen and thorax is very great,
forming no inconsiderable portion of that which supplies
the whole body ; and this fact is of great importance, as
you will presently perceive.

603. When an individual is using great muscular
exertion, in running, leaping, or lifting heavy weights,
the muscles of the chest and abdomen are thrown into
violent action, and they necessarily compress the great
cavities of the trunk with considerable force. This
compression squeezes out from the portal and other
internal vessels a large portion of their blood, which
must find accommodations in the blood-vessels of other
parts. Hence the redness of the skin, the flush of the
face, the veins ready to burst upon the forehead, the
blood-shot eye and the giddiness of head attendant on
excessive exertion. Men have been known to drop
down dead with apoplexy while attempting to raise
great weights. The quantity of blood forced from the
chest and abdomen has proved too much for the delicate
vessels of the brain; they have yielded, and inevitable
death has instantly succeeded.

604. Now what opinion can you form of the reason-
ing faculties of one who has been informed of these
facts, and still continues to encase the chest and abdo-
men in a tightly drawn garment of complicated canvass,
wood, steel and whalebone, in order to improve upon

260 OF THE GREAT CAVITIES.

the model on which Providence has formed the species,
— the form which the Creator made in his own image?
What must be the consequence of a perpetual compres-
sion depriving the digestive and respiratory apparatus
of their proper supply of blood, while it forces this fluid
in inordinate quantities into the capillaries of the brain,
leaving it to stagnate there by suppressing the freedom
of the circulation ? Excuse me if I prove a liltle severe,
but the question should be answered. If constitutional
silliness be not the first cause of tight lacing, the con-
tinuance of this folly will assuredly produce that un-
desirable accomplishment in a reasonable time, by de-
priving the brain of its proper exercise and nutriment.
Corsets, properly regulated, and worn during certain
portions of the day, may be both useful and necessary
in certain stages of disease, deformity or debility, but
those who wear them tightly laced for the purpose of
improving a natural figure, are excusable only on the
ground of a species of ignorance which a very slight
knowledge of physiology must inevitably dispel. Among
the evils following this abominable habit and dependent
upon the effects of pressure just described are, indiges-
tion, the conversion of a beautiful colour into a red and
glaring spot upon the cheek in which the distended and
diseased veins are distinctly visible, habitual inflamma-
tion, weakness and discoloration of the eyes, melancholy,
distressing headache, and even swelling of the feet. Of
other evils following the same custom, I shall have oc-
casion to speak hereafter, though the catalogue seems
long enough already.

261

CHAPTER XIII.

OF THE MECHANISM OF BREATHING.

605. The process of breathing consists of two parts,
the inspiration or inhalation, and the expiration or exha-
lation— terms needing no definition. In the effort of
inhalation, the cavity of the chest is enlarged by mus-
cular action, and the air rushing in through the trachea,
expands the lungs to an equal extent. In exhalation, the
chest collapses, partly by its own weiglit, and the air is
forced out again through the trachea. But this process
is also aided by the muscles, and in rapid or difficult
breathing, the muscular action is all important and often
very powerful. Let us examine the history of these
processes.

608. The spine being supported and the head held
erect by the muscles of the back, the two upper ribs, the
sternum, and the shoulders are properly supported by the
muscles passing from the head and the cervical verte-
brae. When we perform an easy inhalation, these mus-
cles contract very gently, and the ribs, sternum, and
shoulders are slightly elevated by their action. As the
ribs tend obliquely downwards (474), they cannot be
thus elevated without widening the distance between
their cartilages and the spine, and carrying the sternum
also forward. This evidently enlarges the cavity of the
chest, but only to a very slight extent.

607. But while the muscles of the neck are thus con-
tracting gently, the intercostal muscles are also in ac-
tion. The second pair of ribs is drawn a very little
nearer to the first, and all the succeeding pairs must
rise with it. Now, while this is going on, the third pair
are drawn nearer to the second by the same means, and
of course all the succeeding pairs are elevated again by
this contraction. That is, the third pair is elevated
22*

262 OF INHALATION AND EXHALATiON.

about twice as far as the second. Now as the same
kind of contraction takes place throughout the whole
series of twelve ribs, it is evident that the lower pairs of
ribs are elevated many times farther than the first pair.
But the lower ribs are placed much more obliquely than
the upper ones, as you may perceive by reference to
Fig. 49. page 211. The former pairs must therefore
sweep much more widely from the spine as they rise
than the latter ones. Thus, the lower part of the chest,
where the principal bulk of the lungs is formed, is much
more considerably dilated in inhalation than is the upper
part. Now as the sternum must follow the motions of
the cartilages of the ribs on which it hangs, it is tilted
forward very much at its lower extremity, while its
upper end remains almost at rest.

608. You perceive at once, then, that every thing
which binds the lower ribs must interfere much more
seriously with breathing than a similar restraint near
the summit of the chest. But if you wish to ascertain
how important is the motion of even the upper portion
of the thorax, you have only to sit for half an hour
leaning over your desk, with your head bowed forward,
so as to relax the muscles of the neck, and thus deprive
the superior ribs and sternum of their natural share in
the process of breathing, and if you do not feel prompted,
by that time, to sigh over your error, there is little de-
pendence to be placed upon physiological laws.

609. But the ribs and sternum, with the muscles at-
tached to them, are not the only parts interested in the
effort to inhale. You remember the position of the
diaphragm, placed like an inverted basin projecting into
the chest from the edges of the false ribs, the spine and
the ensiform cartilage, with the lungs and heart lying
on its upper surface, and the liver and stomach filling
up its cavity. This great muscle, which, while the
lungs are empty, projects very high into the chest, as it
is represented in Fig. 58. 1, 1, contracts on the instant
of inhalation ; and, driving the abdominal viscera and
dragging the heart and pericardium downwards, ren-
ders the abdomen more prominent, as it is represented

MECHANISM OF BREATHING.

263

in fig. 55, 2. To permit this change, the abdominal
muscles are relaxed during inhalation. The contraction
of the diaphragm flattens the basin or renders it more
shallow, and brings it to the position seen in fig. 55, 1,
and the cavity of the chest is thus enlarged to a great
extent, as you may perceive by comparing the two ac-
companying figures with each other.

Fig. 55. Fig. 56.

Fig. 55. Aiitero-posterior section of the thorax when the lungs
are distended.

Fig. 56. Antero-posterior section of the thorax when the lungs
are empty.

], 1. Tlie diaphragm. 2, 2. The muscular walls of the abdomen.

610. Having now described the mechanism of inhala-
tion, let us consider that of exhalation. The inhaled air
having answered the purpose for which it is admitted,
and being charged with moisture and carbonic acid,
requires to be expelled. For this purpose, all the mus-
cles previou.sly called into action are relaxed ; the
weight of the chest drags the ribs downward and con-
tracts the cavity ; this change is aided by the tonicity
of the abdominal muscles, now no longer resisted by the
activity of the diaphragm, and the abdominal viscera
are forced upward by the pressure resulting frbm this

264 MECHANISM OF BREATfllNG.

tonicity, and thus the depth of the basin of the diaphragm
is rendered as great as before, and the heart is elevated
to its former position. In other words, the form of the
abdomen and thorax is restored from the condition re-
presented in fig. 55, to that displayed in fig. 56.

611. Thus you see that the muscles of the abdomen
are not less interested in respiration than those of the
chest, and that neither of these sets of organs are capa-
ble of acting with full effect unless those of the neck
and back be also in a healthy condition and in a proper
attitude. A disease of the spine that compels a patient
to curve the back, or a habitual stoop, are calculated to
injure health and enfeeble the mind by embarrassing
the process of respiration, and thus rendering impure
the blood which nourishes the frame, supports its func-
tional powers, and stimulates the brain to full activity.
Even the motions of the abdominal viscera and the
heart, produced by the rise and fall of the diaphragm,
promote digestion and give vigour to the circulation. I
mention these circumstances as illustrations of the man-
ner in which one part of the frame depends upon an-
other, and in proof of the complexity of those seemingly
simple functions with which the ignorant so often ven-
ture to tamper.

612. When respiration is rendered dilficult by disease,
the abdominal muscles are often much more powerfully
exerted in effecting exhalation. If the intercostal mus-
cles be attacked by spasm, as is the case when we are
affected with what is called " a stitch in the side," the
breathing is carried on by the diaphragm*; and this is
also the case when the cartilages of the ribs become
ossified in old age. On the contrary, in some rare
cases, the diaphragm labours under rheumatism or ner-
vous disease ; and the patient, who then suffers excru-
ciating agony upon every motion of the muscle, endea-
vours to keep it at rest, and breathes almost exclusively
with the ribs and sternum. When any of the more
important abdominal viscera are inflamed, the same
effort is made to prevent the diaphragm from disturbing
the inflamed part. Such diseases of the abdomen may
be sometimes detected by the short, quick, and imperfect

EFFECTS OF MECHANICAL RESTRAINT. 265

breathing, even when the patient is deranged or insensi-
ble. In these cases, the muscles of the neck act power-
fully in the endeavour to raise the upper ribs, and even
the countenance is distorted by the exertion.

613. If the ribs be confined by a tight garment, it is
obvious that respiration must be carried on by the dia-
phragm alone ; and, by a law with which you are
already familiar, this must give that muscle undue
strength, while it weakens the intercostal and other
muscles of the chest (475, 476). The moment the gar-
ment is removed, the ribs feel the want of proper mus-
cular support, and fail to perform properly their function
in assisting to support the sternum and the spine. In
consequence of this the shoulders fall, and the back be-
comes distorted. When the habitual pressure is very
great it ev-en modifies the form of the ribs, indenting
them or producing a narrowness of the lower part of
the chest, which for ever forbids that perfect respiration
necessary to vigour either of body or mind.

614. But the corset, so universally employed as an
article of female attire, is made to embrace the abdo-
men as well as the thorax, and when at all tightly
laced it must inevitably prevent those changes in the
position of the abdominal viscera (609) without which
it is impossible for the diaphragm to descend, and thus
all the parts interested in the process of inhalation are
seriously embarrassed in their action. The effects of
this embarrassment are obvious to all well-informed ob-
servers in the straining of the neck, and the laborious
heaving of the shoulders, which betray the folly if not
the wickedness of the victim of fashion. It is impossi-
ble for the blood to be properly purified under such cir-
cumstances, and in addition to the evils already pointed
out when considering the effects of pressure on the
great cavities (603), I may mention that many of the
nervous affections, such as neuralgia and even con-
vulsions, so often witnessed in young females, are
caused or very much increased by the action, upon the
nervous system, of the impure blood thus forced into
circulation.

266 MECHANISM OF BREATHING.

615. One of the worst consequences of the habit of
tight lacing, is the seeming necessity of continuing the
use of the corset at all times, whether in full dress or
undress. By preventing the proper motions of the
abdominal muscles and the diaphragm, this instrument
enfeebles those important organs and diminishes their
tone. Immediately upon its removal, therefore, the
diaphragm descends, and fails to support the heart in
its proper position. Hence occurs a dragging sensa-
tion or that of heavy weight in the chest, generally
accompanied by distressing palpitations. Meanwhile
the abdominal viscera not being compressed sufficiently
by the walls of the cavity in which they are placed,
perform all their functions imperfectly. Hence follow
indigestion, lassitude, and a long train of highly danger-
ous results, driving the patient to the reapplicationof
the cause of all this mischief.

616. Without prohibiting the proper use of the cor-
set under surgical advice in certain cases of debility,
and bowing to the conventional regulations which ren-
der its moderate use indispensable when in full dress, I
would urgently recommend the gradual relaxation of
the cords of those who are so unfortunate as to have
established the habit of tight lacing, and even to those
who use the article more discreetly I would remark
that vigorous health can only be obtained by rejecting
it altogether during the early part of the day, while
employing active exercise. To children while growing
the use of the corset is exceedingly fatal, and an
indulgence in tight lacing is madness in those who
wish to advance in their scholastic studies with ra-
pidity.

617. You have been informed, in one of the earliest
chapters, that even in man the skin is capable of carry-
ing on a certain amount of respiration, and if this be
checked by carelessness, the lungs are m.ade to undergo
too much exertion, and must be ihereby rendei'ed more
liable to disease. After this remark it is needless to
impress you more fully with the great importance of
cleanliness as a means of promoting health.

267

CHAPTER XIV.

REMARKS ON DIGESTION AND THE CIRCULATION.

618. It seems proper here to offer a few remarks
connected with digestion and the circulation, which
furnish but so many illustrations of principles already-
laid down in this little volume.

619. The first preparation of food for admission into
the frame consists in its proper mastication. The pre-
sence of the food in the mouth., and the muscular efforts
exerted in chewing stimulate the salivary glands situated
about the mouth, and induce them to pour into that
cavity an increased quantity of their peculiar secretions.
In order that the stomach should act properly upon the
solid portions of food, it is necessary that the latter
should be divided into very small portions, and each
portion requires a coating of saliva, not only to facili-
tate its passage down the oesophagus, but to assist in
dissolving it. The solvent powers of the saliva are
truly astonishing, for it is capable of slowly eroding
almost every substance, except, perhaps, glass, platina
and the enamels, such as those of which artificial teeth
are constructed. Even gold, unless very pure, does not
entirely resist its action.

620. You may judge, then, how trying to the vital
power of the stomach must be the disgusting habit of
bolting provisions in the manner for which our country-
men are so unenviably distinguished, and you may also
infer some of the ill consequences of the use of tobacco,
which exhausts the saliva, and, by constantly stimulating
the glands to undue activity, vitiates its quality.

621. As an additional proof of the importance of
mastication, it may be mentioned that large portions of
solid matter taken into the stomach cannot be moved
with sufficient ease from one part of the cavity to an-

268 PROCESS OF DIGESTION.

Other, in order to bring all portions of the food succes-
sively under the full influence of the coats of the organ
by which the function of digestion is carried on. When
fresh milk is taken rapidly and in large quantities, it
coagulates in one mass, and cannot be broken down for
a long time by the stomach, and it is therefore extremely
difficult of digestion. But when formed into curd and
then masticated, or when boiled for a few moments
with a very little flour or bread, which prevents it from
coagulating, it becomes an agreeable article of diet even
to those who dare not employ it in its ordinary state.
Under the pressure of starvation, on wrecks or in boats
at sea, when the mariner is driven, through dire neces-
sity, to prey upon the bodies of his fellow-sufferers, men
have been known to slake their horrible thirst with large
draughts of human blood. This forms a very firm co-
agulum, which would be regularly digested if broken in
pieces, but is perfectly indigestible in the mass ; and
the death of the individual almost always follows his
rashness.

622. Arriv^ed in the stomach, the food is subjected to
the action of other solvents besides the saliva. A pecu-
liar secretion from the coats of the organ, known by the
name of the gastric juice, and thrown out whenever food
enters, is the principal agent in this business. It has the
power of preventing the food from being decomposed
by the heat of the stomach, as it would be in the open
air, under the same temperature. But this power is
lost wholly, or in part, not only in many diseases, but
in cases of general debility, weakness of the abdominal
muscles (615), or loss of tone in the muscular fibres of
the stomach. This accounts for the rejection of food
so often occurring in dyspepsia, and shows the cruelty
frequently exercised towards the young and feeble by
silly nurses and robust guardians, when they press their
charge to eat though they have no appetite, or to subsist
upon food that proves disgusting from peculiarity of
taste. These things are natural indications in most
instances of the condition of the health, and cannot be
entirely disregarded with impunity. I have enlarged

PROCESS OF DIGESTION. 269

upon this subject in another volume, which may, some
da}-, fall into your hands.*

G:23. The stomach acts first upon those parts of the
food which lie next its walls, keeping the undigested
mass in the centre. As layer after layer of chyme is
formed, it is carried to the pylorus by the vermicular
motion produced by the muscular fibres of the stomach,
and passes through that orifice into the duodenum, until
the process of digestion is complete.

624. The first steps in digestion seem to require the
greatest exercise of vital power, and while they are
accomplished, the nervous energy of the organ, as well
as the quantity of blood contained in it are much in-
creased. Hence eating is generally followed, first by a
chill, the result of the calling of the blood from the sur-
face, and then by a fever, owing to the rapid action of
the heart in quickening the circulation (274). All
exertion, whether of mind or body, should be avoided
at this time, that the powers of life may not be called
oft' in other directions to the disturbance of digestion
(276). At least an hour of rest should be allowed after
our principal meal, if it be possible. Those of you who
endeavour to study a diflicult subject immediately after
dinner will understand what I mean. The half dreamy
luxury of the siesta at this time promotes health in per-
sons who have reached middle life ; but, except in de-
bilitated individuals, the vital functions are too active in
the young to require such absolute repose, and that is
idleness in them which may be almost a necessity with
their parents.

625. Water seems to be taken up or absorbed very
rapidly by the veins of the stomach, and enters the cir-
culation almost immediately ; but the dissolved solid
portions of food are not thus absorbed, and must pass
into the small intestines, to be there taken up by the
lacteals.

62G. Having passed into the duodenum, of which the

* Popular Medicine, or Family Adviser. Philadelphia, 1838. Pub-
lished by Carey, Lea and Blanchard.

270 PROCESS OF DIGESTION.

functions seem to bear some analogy to a second
stomach, the more nutritive parts of the chyme are
converted into chyle by the action of the bile and the
pancreatic juicCc It is then prepared to enter the cir-
culation, and the whole mass driven forwards into the
other portions of the small intestines by the successive
contractions of the circular muscular fibres of the canal
behind it, and their relaxation in front. This peculiar
motion of the intestines is called the peristaltic motion.

627. When certain poisons or very irritating sub-
stances are received into the stomach, or secreted there
in consequence of disease, they often produce vor^iting.
In this effort the pylorus is closed as by a spasm ; the
vermicular motion of the fibres of the stomach is re-
versed, and its contents urged towards the cardiac
extremity. An involuntary violent and sudden contrac-
tion of the stomach, and of the abdominal muscles also,
then ejects the contents through the oesophagus. If this
effort be frequently repeated, it is found that the peristal-
tic motion of the duodenum is reversed, and its contents
are thus forced upward through the pylorus into the
stomach. But the agitation and strong pressure of the
abdominal muscles in vomiting empties the gall-bladder
into the duodenum. The bile then commonly enters the
stomach in consequence of the reversed action of the
fibres. This f]uid, which, as you have been informed, is
the natural purgative, has no business in the stomach,
and when admitted there, it acts as a powerful emetic.
This keeps up the vomiting, rendering it more and
more distressing, until the gall-bladder is entirely emp-
tied. Now, although emetics are useful remedies in
certain cases, you see at once the folly of the popular
notion that the discharge of bile produced by them, is a
proof that the patient is " hilious,^^ and the remedy, there-
fore, proper. Emetics are much too frequently and too
lightly used without advice. If the discharge of bile
be a proof of biliousness, the medicine w^ill always pro-
duce the disease if taken by a healthy man.

628. It is unnecessary for me to trace out the course of
the food through the small intestine into the great intes-
tine, whence the valve already described (596) prevents its

STRUCTURE OF THE BLOOD-VESSELS. 271

return. What most interests us is the nourishment in
the form of chyle, which, being taken up by the lacteals,
soon enters the blood-vessels, becomes converted into
blood in passing through the lungs, and goes to supply
new particles to all parts of the frame, as well as mate-
rials for the various secretions,

629. Whatever has a tendency safely to accelerate
the circulation, promotes the vigour of all parts ; and I
shall have occasion presently to describe some of the
effects of exercise in effecting this purpose : but it is
necessary to premise a few words upon the structure of
the blood-vessels.

630. You have been informed (261), that the heart
and arteries are lined internally, throughout their entire
extent, by a thin membrane, which is doubled upon itself
in certain places so as to form regular valves ; as, for
instance, between the auricles and ventricles of the heart
(261), and at the origin of the great arteries (262).
This membrane bears much resemblance to those called
serous ; such as the peritoneum and the pleura. It also
lines the capillaries, and, passing into the veins, fur-
nishes them with an internal coat, and forms all the
valves already mentioned as pecuHar to those vessels
(see fig. 29, page 97). Though strengthened by other
coats in most places, this membrane is all that is abso-
lutely essential to the structure of a blood-vessel. In
the solid parts of the bone, where no external protection
to a vessel is necessary, it is said that the veins are
composed exclusively of this internal coat, which indeed
is little else than one great cell of cellular tissue, with
innumerable branches connected together in a complete
net-work.

631. But so delicate a membrane would be perpetually
liable to being torn or burst, if it were not strengthened
by some firmer protection. In the bones, the firm
earthy matter supplies this support, but every where
else the blood-vessels are provided with a thick, firm,
external coat, composed of fibrous cellular tissue, which
is so strong in the arteries that these vessels do not even
collapse when empty.

272 PHENOMENON OF FAINTING.

632. These two coats are sufficient for the veins,
"which are almost passive canals for the conveyance of
the blood towards the heart; but the arteries and capil-
laries take a very active part in directing the route and
determining the rapidity of the circulation. For this
purpose they are provided with a third coat, placed
between the other two, and composed of very contrac-
tile fibres, resembling in function the muscular fibres of
the alimentary canal (368). When cold is applied to a
part, these fibres are stimulated to contract : less blood
reaches it, and it becomes benumbed and, pale, in con-
sequence of the diminished supply of blood to the
nerves (311). When an injury happens to a part, these
fibres relax themselves, more blood flows through the
vessels, and the sensibility of the part is heightened.
Thus you see the weakness of one part becomes an
immediate source of strength to another, and the re-
verse. This principle applies to the history of all
stimulants that are local in their action.

633. It is by means of the tonicity of the fibrous coat
of the arteries, then, that the blood-vessels adapt them-
selves to the ever-varying amount of their contents, and
furnish to each part of the body the amount of blood
that its particular condition at the time requires. It
is by this power that they raise the blush of emotion on
the cheek, send additional supplies to a wounded part
to enable it to heal, and propel their fluid to the stomach
after dinner for the purpose of digestion. If we draw
blood so rapidly as to empty the arteries faster than
their fibrous coat can contract, the patient faints. The
heart continues to palpitate, slowly, and by habit, but it
cannot urge the fluid forward through an empty hose,
nor can the veins continue to refill it, while the arteries
are unable to force the fresh supplies of blood into those
canals. The patient would never recover, were it not
that the arteries continue to contract even during his
insensibility, and at length they press upon their remain-
ing contents with sufficient force to allow the heart to
renew the circulation. Fresh blood then reaches the
brain again, and the faculties revive. So great and so

EFFECTS OF EXERCISE ON THE CIRCULATION. 273

durable is the contractility of the fibrous coat, that in
the act of death they completely obliterate the canals
which they surround, and although they relax them-
selves again at the last moment of departing life, they
are found completely empty in the dead body ; all their
blood being expelled from them into the, veins.

634. The veins are far more numerous than the arte-
ries. In most parts of the body, each principal arterial
branch is usually attended by two venous branches. In
the extremities, and the walls of the great cavities, many
of the veins j)ursue their course among the muscles at a
distance from the surface, while another set are found
almost immediately beneath the skin. When we use
long continued and powerful exertion, the muscles com-
press the deeper seated veins, and embarrass the circu-
lation in that direction ; but the superficial veins then
become distended, and thus supply the deficiency.

635. Moderate and varied exercise, on the contrary,
promotes the flow of blood through the deep-seated veins,
by a most beautiful mechanical process. As the muscles,
in such exercise, are alternately contracted and relaxed,
the veins which they cover are alternately emptied by
their pressure, and again suffered to become filled. Now
while they are momentarily compressed, the blood can-
not flow backward towards their extremities ; for this
motion is prevented by the valves, (184). It is therefore
urged suddenly forward in the direction of the heart,
whence other valves prevent its return. The empty ves-
sels then offer no opposition to the entrance of fresh
blood from their branches, for they are not allowed time
to contract and diminish their size, and they become fill-
ed instantly when the muscle is relaxed.

636. The constant repetition of the process just de-
scribed produces a very rapid and constant current to-
wards the heart. The heart being filled more readily
than usual by this means, beats much more frequently
in a given time, and hastens the circulation throughout
the frame. As a necessary consequence of this state of
things, more blood flows through the lungs, and in order

23*

274 EFFECTS OF EXERCISE ON THE CIRCULATION.

to purify it, the breathing is rendered very rapid. Every
part of the frame thus receives more nourishment, the
colour of the blood is heightened, and life and vigour
are increased in every organ. Such, you are aware, are
the common results of active exercise.

637. This increased energy of the circulation may
prove dangerous when any particular organ is already
in a state of too great activity, for it may then be stimu-
lated beyond its capacity of endurance, and disease may
follow. For the same reason we enjoin absolute rest in
cases of severe inflammjation ; for, in such cases, it is
our desire to lessen the excessive vital energy in the part
by restraining the force of the circulation. Much mis-
chief has been done by ill-regulated exercise, employed
without due reference to the condition of internal parts.

638. It often happens that persons in a state of ex-
treme debility require the benefits of exercise when they
are unable to endure the fatigue. It is easy to produce
similar changes in the circulation, even while the patient
lies in bed, by acting on the superficial veins. Frictions
on the surface evidently bring about the same result with
exercise, and no doubt much of the great benefit result-
ing from their application in convalescence from disease
is due to this cause. The irritation of the skin which
they occasion is also beneficial, by invigorating that im-
portant membrane ; but the use of the flesh-brush or
coarse towel is often too severe to be borne if long con-
tinued, and the effects of rubbing with the palm of the
hand, or other very soft substances, have been much ne-
glected by writers on the art of preserving health.

639. I am not at liberty to suppose that you are yet
sufficiently acquainted with the principles of mechanics
to comprehend fully the manner in which passive exer-
cises, such as swinging, riding on horseback, sailing, and
many other quiet amusements produce the same effect
on the circulation with the operations mentioned in the
four last paragraphs ; but if you understand thoroughly
the nature of inertia, momentum, the centrifugal force,
and elasticity, you will be able to follow out a chain ot

ON THE PROPER FUNCTION OF A NERVE. 275

reasoning on this subject as successfully as I could do.
You will have only to recollect that the veins are elastic
tubes, furnished with frequent valves, permitting their
contents to pass only in one direction, and the character
of the exercise will explain the consequences.

CHAPTER XV.

ON THE FUNCTIONS OF THE NERVES AND BRAIN.

640. I MUST now request you, to re-peruse with care,
the entire chapter on the nervous system, in the first
part of this volume (chapter viii. page 139), in order
that the conients of the present may be rendered intelli-
gible, without tne necessity of repeating definitions and
references.

641. In the chapter just referred to, I have said that
in the higher orders of animals, the nerves preside over
the functions of the parts to which they are distributed :
but this language, employed for the sake of convenience,
may mislead you, as I believe it has done many philoso-
phers, unless some further explanation is added. Even
the expression that the nerves are media of communi-
cation or post-roads between one organ and another,
is allegorical. We have no legitimate reason for be-
lieving that any thing actually passes along these solid
cords when distant parts act upon each other through
their mediation ; and the doctrine of the existence of a
nervous fluid, about which you will find physiologists
continually talking when you read more extensively
upon the subject, is a pure hypothesis — an apology for
our ignorance.

642. If we take our examples from the nervous sys-
tem of organic life, of which the branches do not com-
municate any impression to the consciousness .of the
individual, all we know of their functions is simply this :

276 ON THE PROPER FUNCTIOJV OF A NERVE.

the peculiar condition of the organ situated at one ex-
tremity of a nervous fibre, produces such a condition of
the nerve itself, that the organ or organs with which the
fibre comnnunicates at the other extremity are changed
in their condition also. An action on the nerve at its
commencement, causes it to act on the parts in which
it terminates. We do know that the nerve is the agent
by which this mutual relation of distant parts is secured ;
for, if the nerve be divided, the relation ceases. This
power of perceiving an impression made upon it by ah
influence external to itself, and consequently creating a
corresponding influence upon some other part also ex-
ternal to itself, is the peculiar province of a nerve. It
is safe, then, after this explanation, to say, in allegorical
language, that the nerves receive impressions from one
part and convey or communicate them to another.

643. Now every nervous fibre has its own proper
function. The nerve of sight does not convey sounds,
nor does a nerve of feeling convey impressions of taste.
You will be somewhat startled, perhaps, to hear it as-
serted, that the feeling of the elbow is a different sense
from that of the finger, yet I think it may be easily
proved, as we shall presently see.

644. The function of a nervous fibre resides not ex-
clusively in its extremities, but dwells in all the interme-
diate parts, though, perhaps, not in so great a degree.
The extremities have more susceptibility than the trunk.
To explain this point, it is best to take an example from
the nerves of feeling; for, as they communicate directly
with our consciousness, we can m.ore readily observe
the manner of their action. Nothing is more common
than for a patient who has had a limb amputated to
complain for many days of pains in the part that has
been removed or destroyed. " Doctor," he will say,
". I have a severe cramp m my toes to-day," forgetting
at the moment that those toes are beneath the soil or
preserved in an anatomical museum ! Now the mean-
ing of such complaints is simply this: an irritation takes
place on the stumps of some of the fibres of a particular
nervCj at the place where the limb has been amputated.

ON THE PROPER FUNCTION OF A NERVE. 277

This may result from inflammation in the part, from the
pressure of the dressings, or from the dragging back of
the divided muscles as their tonic contraction renders
them shorter. Such causes lead to sensations in the
mind precisely similar to those which would have fol-
lowed analogous injuries inflicted upon the extremities
of the same fibres, had the limb not been lost ; and the
mind, receiving the same impression from the nerve that
it would have received had the toes been injured, natu-
rally refers that impression to the spot to which the nerve
was designed to pass. You see, then, that it is the func-
tion of the whole nervous fibre of feeling belonging to
the point of the elbow to convey to the mind the sensa-
tion of feeling at the elbow ; and so likewise, the nerve
of feeling of the finger conveys only the sensations
proper to the finger, — which distinct functions they con-
tinue to perform for a certain time, even if elbow and
finger have both lost their existence. That they soon
lose this power after amputation, is most true ; but this
results from the general physiological law, that parts
which are rendered useless, soon lose or change their
functions for want of appropriate exercise. Some of
the evidences of a similar character, presented during
disease, are very curious, and tend to show the folly or
wickedness of those who undertake to tamper with
human health, without a deep knowledge of anatomy
and the principles of physiology. In that dreadful com-
plaint, called " hip-joint disease," one of the first symp-
toms is a pain in the knee, where there is absolutely no
real ailment : and had I time and space, it would be
easy to quote a hundred similar instances.

645. As it is the function of a nerve to communicate
the influence of external things (among which things,
external with relation to themselves, we may rank the
organ in which they terminate) to certain organs of
the living body, in order to influence the actions of those
organs, we might reasonably suspect that the nerves
may communicate impressions one to another, as they
do to the muscles and other parts. That this is the fact,
is shown by the history of the ganglions and plexus, as

278 ON THE PROPER FUNCTION OF A NERVE.

given in chapter viii. Hence results the endless com-
plexity coupled with the beautiful conformity of motion
observed throughout the animal frame.

646. The only nerves that communicate impressions
directly to the mind, or receive impressions from that
source, are the nerves of sensation and those of volun-
tary motion. The former are usually considered as in-
cluding only the nerves of what are commonly called
the five senses, — sight, hearing, taste, smell, and tact,
touch, or feeling. The nerves of touch or feeling, for
the most part, appear to originate from the spinal mar-
row, like those of voluntary motion; but those of the
other senses, with the exception of smell, are seemingly
derived from the brain near the spot where the spinal
marrow, somewhat changed in structure and called
the medulla oblongata, terminates in that portion of the
nervous system. The portion of the nervous system
which presides over the sense of smell is very peculiar
in structure, but the details are foreign to our present
purpose.

647. When we come to examine the question strictly,
we find that the nerves of the five senses have really, of
themselves, no sensation whatever: for if you divide a
nerve of feeling, the part of it which is cut off from the
brain becomes instantly incapable of feeling. You may
make this division as near the origin as you please,
yet the result will be the same. In the same manner,
you may prove that the eye does not see, nor the ear
hear; for both these organs may be perfect in organi-
zation, yet they are rendered perfectly useless if the
optic nerve of the former, or the auditory nerve of the
latter be cut off at its origin by disease or accident. It
is customary with many physiologists, then, to say that
these nerves report or convey all their impressions to
the brain, and the inference is apparently plain that it
is the brain that sees, hears, and feels. Let us examine
what is the brain, and what are its functions.

648. The brain, of which something has been said in
chapter viii. (284, 285, 286), is a great mass of ner-
vous matter filling the entire cavity of the cranium,

OF THE BRAIV AND ITS MEMBRA XES. 279

(399) and enveloped in several mennbranes. When we
remove the top of the craniunfi, in a dead animal, we
first encounter a thick, strong, fibrous membrane, fur-
nished with many blood-vessels, and acting as an inter-
nal periosteum to the cranial bones. This is the dura
mater (421). It extends throughout the spinal canal,
thus enclosins^ that cavitv and the interior of the cranium
as one undivided chamber.

649. The dura mater presents us with a curious pro-
cess called ihefalx or sickle, the blade of which instru-
ment it strongly resembles. This process partially
divides the cavity of the cranium into two chambers.
It consists simply of a curtain formed by a doubling of
the membrane, and is suspended from the middle line of
the arch of the cranium. It is very narrow at its com-
mencement from the ethmoid bone (419), just within the
root of the nose, but becomes broader and broader as
it sweeps upward, along the middle of the frontal bone
(400), backward, along the suture joining the two pa-
rietal bones together (406), and downwards along the
upper limb of the cross of the occipital bone (410, 411,
412), to the centre of that cross, where it is quite wide
like the heel of the blade of the sickle. Here it joins
with, or is continued into two similarly constructed cur-
tains, which lie horizontally and extend along the two
lateral limbs of the occipital cross to the temporal bone,
and are even attached to the angular edge of the petrous
portion of the bone (414). These horizontal curtains,
taken collectively, are called the tentorium.

650. The tentorium is the membranous floor on which
rests the posterior part of the cerebrum or greater brain,
and separates it from the cerebellum or lesser brain (412).

651. A narrow curtain of the same character extends
from the lower surface of the tentorium, along the lower
limb of the occipital cross, to the great occipital fora-
men (409). It is called the lesser falx.

652. Thus you see that the arch of the cranium is
divided into four great compartments, by the partial
partitions formed by the falces and the tentorium. The
two upper compartments are occupied by the cerebrum,

280 OF THE BRAIN AND ITS MEMBRANES.

separated into two similar halves, called the right and
left hemispheres, by the greater falx. The two lower
compartments are occupied by the cerebellum, similarly
separated by the lesser falx.

653. When the dura mater is cut away, we come
next upon the serous membrane of the head, called the
arachnoid or spider-web membrane, from its extreme
delicacy. It is transparent, and so thin that anatomists
are often puzzled to separate it from the parts beneath.
It is spread smoothly over the general surface of the
hemispheres, enters and lines several cavities within ihe
brain, and follows the spinal marrow to its termination.

654. Through this membrane, and the one immedi-
ately beneath it, we see the surface of the brain, which
is every where varied in surface, so that it looks as if
composed of a long tube, like the intestines, folded and
winding upon itself, in order to occupy as little space as
possible. These turnings of the surface are called the
convolutions. They are more complicated and numerous
in the more lofty animals and at mature age, than in the
humbler animals and in the young.

655. Beneath the arachnoid membrane we have the
pia mater, or proper membrane of the brain, which em-
braces the cerebral substance very closely, following all
the irregularities of the surface, and dipping into every
depression between the convolutions. The pia mater is
full of large blood vessels, and supplies the substance of
the brain with all its capillaries. It then descends along
the spinal canal, performing the same office for the
spinal marrow, and furnishing the proper covering or
neurilema (289) to every nerve as it quits the canal. In
one sense, then, it may be regarded as the natural en-
velope of the whole nervous system.

656. The pia mater being removed, we come to the
naked brain. In figure 57, you are presented with a
view of the lower surface of this part of the nervous
system, with many important nerves originating from
it. You observe that each hemisphere of the cerebrum
is divided into three lobes. The anterior lobe, a, lies
over the eyes, in that depression of the base of the era

OF THE BRAIN AND ITS DIVISIONS.

281

nium (399), marked^, fig. 42, at page 183. The middle
lobe, b, occupies the depression marked h, m the figure
to which I have just referred. The posterior lobe, c, c,
lies on the upper surface of the tentorium, and fills that
portion of the cranium which lies above the centre of
the occipital cross (c, fig. 42). The superior surface
of the cerebrum does not present this lobulated appear-
ance, but conforms to the regular arch of the skull.

Fig 57.

282 INTERIOR STRUCTURE OF THE BRAIN.

657. At d, d, you see the two hemispheres of the
cerebelluQi, which, lying under the tentoriunn, fill up
those deep depressions, one of which is marked i, fig. 42,
that lie below the horizontal limbs of the occipital cross.
The convolutions of the cerebellum are much smaller
and proportionally more numerous than those of the
cerebrum, as you will perceive on reference to the
figure.

658. The letter e, designates the extremity of the
spinal marrow, cut of^^ just where it enters the head ; /
is a very peculiar extension of cerebral matter lying on
the cribriform plate of the ethmoid bone, and usually
termed the olfactory nerve ; h represents the optic nerves
or nerves of sight, dividing at the place where they enter
the orbit of the eye ; i is one of the large blood-vessels
of the brain ; and k represents a rounded mass chiefly
of medullary matter, placed at the junction of the cere-
brum with the cerebellum and the spinal marrow. The
white fibres represented as springing out from near the
middle line of the base of the brain, represent the origin
of as many nerves which pass out of the cranium, and
are distributed to various parts, but chiefly to the head,
face, and the organs of the special senses.

659. After this hasty glance at the outside of the
brain, let us peep into the interior. The nature of the
cortical or cineritious, and the medullary matter have
been explained already (283, 284), and you will remem-
ber that the latter is composed of regular rows of glo-
bules, precisely like all other nervous fibres, except that
they are not provided with a neurilema. Each of them
constitutes then, a nervous fibre in the condition in
which it is found within the substance of a ganglion.

660. But the only change in the situation of nervous
fibre, while divested of its neurilema and passinfr through
a ganglion, appears to consist in its being brought more
nearly within the influence of the surrounding fibres, so
that the diseases and accidents of the one may produce
morbid eflfects or healthy impressions on the other. There
exists no fact which will warrant us in supposing that
the peculiar function of a nervous fibre is ever essen-

ON PHYSICO-MENTAL FUNCTIONS. 283

tially changed in character, even within a ganglion, un-
less it come into contact with cineritious nnatter, and
derive from it an addition to its substance.

661. All the fibres of the brain originate or terminate
in cineritious matter, and those which come from or
pass to the different parts of the body, external to the
cavity of the cranium, appear to have their commence-
ment or their ending in the cortical matter of the surface
of the brain. Now every one of these fibres is a distinct
organ, having its own proper function (643), and nearly,
if not quite, all of them convey to the mind the impres-
sions made upon them by external things, or receive
from the mind the orders of the will ; for they are
nerves of animal life.

662. Some have supposed that the communications
between these fibres and the mind, take place in the
cortical matter where they terminate. But this is im-
possible ; for every surgeon knows that portions of the
surface of the brain are often lost by persons wounded
in battle or otherwise, and yet, in many of the cases, no
part of the body may be deprived of either sensation or
voluntary motion. The integrity of the whole brain,
then, is not necessary to the exercise of consciousness
and will.

663. Consequently, these powers are not functions of
the whole brain.

664. It has been found that if you slice away gently,
one layer of brain after another, in a living animal, you
may remove a very large portion of it without entirely
destroying the evidences of consciousness and will.
There is every reason to believe, from a vast number of
careful experiments, that, but for the general disturb-
ance of the nervous system, (and consequently, of the
functions on which the preservation of fife depends,)
together with the extreme complexity of the organiza-
tion, which prevents us from removing exactly what we
wish without injury to other 'parts, we might continue to
take away all that is essential to the brain, and as long
as a trace remained, some signs of consciousness and
will might still appear. One reason why we fail in such

284 ON rnVSICO-MENTAL FUNCTIONS.

an undertaking, independently of loss of blood and other
causes wiiich destroy the animal before the experiment
can be completed, is, that when we approach the base
of the brain, we inevitably wound the fibres of the spinal
marrow as they enter the brain, and thus cut otl" the
route by which the external senses convey impressions
to the mind : the wliole body is palsied, breathing ceases,
and the animal dies.

6Gd. But enough has been ascertained in this way, to
prove to any dispassionate examiner, that consciousness
and iidll are not functions of any part of the brain in
particular.

666. Now it has been already shown that these
powers of mind are not functions of any other part of
the nervous system, and no one pretends that they are
functions of any other part of the frame. If this train
of reasoning be correct, it follows inevitably that con-
sciousness and will are not functions of the animal
organization.

667. By keeping this in remembrance, j^ou will
escape a thousand errors, into which many dangerous,
though highly important and useful physiological doc-
trines of modern times m.ight otherwise lead you. It is
not a nerve, — it is not the brain that is conscious, — but
the mind ! It is not the nerve or the brain that wills, —
but the mind ! There are those who will tell you that
the will is the result of the combined action and mutual
influence of all the organs, but you are nov/ provided
with a sound physical argument against the doctrines
of these materialists.

668. But if the brain be diseased or wounded, our
will and consciousness are always weakened or led
astray. Why is this ? Because the brain is interested
in conveying to the mind those impressions which arouse
the consciousness, and in carrying from it the orders
issued to the organs. If the diseased or weakened nerve
convey feeble or erroneous impressions, the orders con-
seqiient upon them will be feeble or erroneous. Through
a disease of the nerves of voluntary motion, we may
even idll one thing and do another. Hence, in this state

ON PHYSICO-MENTAL FUNCTIONS. 285

of existence, our mental operations are nnodified by the
perfection or imperfection of our organization, and
though we cannot be justly held accountable for the
false impressions conveyed by our senses, we are ac-
countable when our will is permitted to run counter
to the tenor of those impressions, or when our volun-
tary acts have led to the neglect or injury of the orga-
nization— the machinery — placed under our control by
Providence.

669. There are some, especially among the older
physiologists, who have formed and promulgated the
idea that there is some central spot in the brain, where
all the messages convej^ed by the nerves are ultimately
reported, and whence all the orders of the will are
issued — the peculiar seat of the mind. Descartes placed
it in the pineal gland, a small body in the interior of
the brain which secretes a few grains of a substance re-
sembling sand ! His wild hypothesis is just as dependa-
ble as any other urged on this subject. Were there
any such centre, it would be at some point where all the
nervous fibres meet, but no such spot exists.

670. The cineritious matter of the brain is not con-
fined to its surface, but is found in several places cu-
riously collected into masses intermingled with fibres.
Now, if you turn to the description of the ganglia (29.5),
you will find that this arrangement is essentially the
same with that observed in those organs. Indeed, the
general surface of the brain is constructed on the plan
of a large, flattened, and convoluted ganglion ; and there
is no reason to employ a variety of terms in speaking
of similar things.

671. The brain, then, may be regarded as a great
collection of large ganglia collected together into one
mass, and connected by numerous fibres unprotected by
neurilema. Soft and pulpy as these fibres are, we can
sometimes distinguish bundles of them passing from one
mass of cineritious matter to another, throughout the
substance of the brain ; thus forming regular naked
nerves pursuing a different course from the fibres con-
stituting the great bulk of the medullarv matter in which

24*

286 GRADUAL DEVELOPEMENT OF THE BRAIN.

they are embedded. Each of these bundles must possess
its own peculiar class of functions, for each is a distinct
part of the nervous system. Such nerves are generally
termed commissures, and they are supposed to form con-
nexions between corresponding portions of the two
hemispheres in order to cause them to act in concert.
Many modern discoveries which you are not prepared
to understand are calculated to add probability to this
conclusion.

672. As the health and perfection of the brain — the
principal instrument of the mind — is necessary to the
full display of what we commonly call the mental facul-
ties, you would naturally suspect that the more complex
the structure of the brain of an animal, the greater will
be the vigour of its mental faculties.' Now, so far as
human research has yet penetrated with accuracy, such
is the general result.

673. When we cast a broad glance over the whole
chain of animated nature, we observe that the nerves of
organic life seem to make their appearance before the
spinal marrow, and that this organ is completed before
the brain presents more than a mere rude button on its
summit. Even this button appears to compose chiefly
the rudiment of the cerebellum ; and this lesser brain
reaches a high degree of developement and complexity
of structure, even while the cerebrum continues a simple
smooth mass of nervous matter, with scarcely a trace
of the convolutions to be seen. As we advance towards
the higher classes of animals, the cerebrum becomes
more and more involved in structure, and the closest of
observers are of opinion that this progress of develope-
ment answers very nearly to the order in which the
apparent intelligence of the animal increases.

674. In ascending the series of vertebrate animals,
from the simpler tribes to man, it appears that the cere-
bellum is first brought to perfection ; that the posterior
lobes and the base of the cerebrum are next in pro-
gress ; that the upper portions of the middle and anterior
lobes are superadded in the more lofty creatures (656)

GRADUAL DEVELOPEMENT OF THE BRAIN. 287

but do not reach their ultimate condition until we arrive
at man.

675. The progress of the brain from infancy to man-
hood is well known to be in most respects similar to
this. The base of the brain and the posterior lob.es are
first developed, the middle lobes claim the ascendency
in youth, and the anterior lobes hardly acquire their
full relative size and firmness before the age of thirty
years.

676. The observations mentioned in the four last
paragraphs have induced a very general and natural
belief among physiologists, that the organization of these
several portions of the brain has something to do with
the display of the faculties which distinguish the various
classes of animals ; but, in the hands of a modern sect
of philosophers — the 'phrenologists — this opinion has been
carried out in detail, as I shall presently have occasion
to state.

677. Infancy is governed, like the animals, mainly by
the instinctive feelings ; for it is yet asleep to its respon-
sibilities, and has not acquired more than the rudiments
of its rational faculties. The base of the brain being
then much farther developed than the upper part, is it
not reasonable to conclude that the nervous fibres which
convey to the mind the impressions which awaken the
instinctive emotions are located in that part of the brain ?

678. Childhood and youth are governed mainly by
the moral sentiments and loftier affections ; and in those
states of being, the upper- portions of the middle lobes
gradually approach their highest perfection. If, then,
the mind requires material instruments to call these facul-
ties into play — if the proper organization of the brain be
necessary for their display — are we not warranted in
locating their proper tools in the middle lobes of the
cerebrum ?

679. Manhood is distinguished by the perfection of
the reasoning faculties, and it is that portion of the brain
which fills the cavity of the superior part of the fore-
head— the upper portion of the anterior lobes — that then,
for the first time, acquires its full dimensions and com-

288 OF THE BASIS OF PHRENOLOGY.

pletes the structure of the nervous system. If there he
any part of the brain necessary to the exercise of the rea-
soning faculties^ where are we so Hkely to find it as in
the anterior lobes?

680. If you acknowledge the force of these remarks,
you grant all the fundamental principles of that highest
branch of physiology, called 'phrenology^ which is simply
the science that treats of the functions of the brain. But
phrenology, like all novel subjects of human research,
has been loaded with empirical pretension on the one
hand, and ignorant attack upon the other, till its rational
cultivators can scarcely recognise its features as drawn
either by its professed friends or foes in general society.
I do not propose to initiate you into the details of its
doctrines, much less into the practical application of its
principles to the judgment of character; for if the truth
of the details be acknowledged, their application is so
difficult, and the sources of error so numerous, and as
yet so slenderly investigated even by its avowed advo-
cates, as altogether to unfit it to form part of an elemen-
tary education. He is a bold man who, after long years
of patient study, based upon a thorough professional edu-
cation, ventures to express decided opinions upon cha-
racter on phrenological grounds, or to undertake the
task of opposing the broad doctrines of the science.
But, as it is desirable that every well educated youth
should have some slight conception of the nature of a
subject that has attracted so much attention of late
years, if it be only to guard* him against the ridiculous
mistakes from which even avowed disciples are not
always exempt, I will venture a page or two of illustra-
tion. My remarks will be drawn rather from acknow-
ledged anatomical authorities and the book of nature,
than from the statements of partisans.

681. The spinal marrow — a nervous centre, or rather
centres, belonging to the system of nerves of animal
life — occupies the cervical, dorsal, and a small portion
of the lumbar divisions of the spinal canal (463), the
remainder, containing chieflv the commencements of

INTERIOR STRUCTURE OF THE SPINAL MARROW. 289

the very large nerves of feeling and voluntary motion,
designed to supply the lower portions of the frame.

682. If you divide the spinal marrow horizontally,
you find it to consist of four principal columns of longi-
tudinal, naked nervous fibres, and in the centre you per-
ceive a long mass of cineritious matter, which, in section,
presents the appearance of a Maltese cross. One por-
tion of this cross seems to appertain to each of the co-
lumns of longitudinal fibres.

683. The four columns of longitudinal fibres continue
their course upwards, until they come into the cervical
region of the spine ; and these portions of the nervous
system evidently belong chiefly to the apparatus of sen-
sation and voluntary motion ; though, through the sym-
pathetic nerve, they have many connexions with the
apparatus of organic life.

684. In the cervical region of the spine, two other
columns of longitudinal fibres are superadded, which
are known chiefly to preside over the motions connected
with respiration.

685. It is not unphilosophical, then, to regard the
spinal marrow as four very long ganglions, with two
much shorter ones associated with them at the upper
extremity.

686. These six columns of longitudinal fibres enter
the head together through the great occipital foramen,
where they enlarge themselves into a kind of bulb,
which I have heretofore included in the general de-
scription of the spinal marrow, but which deservedly
bears a distinct name. It is called the medulla ohlon-
gata, and it lies on the cuneiform or wedge-shaped pro-
cess of the occipital bone. Fig. 57, e.

687. At this point the fibres of the several columns
intercross each other from opposite sides, and become
intermingled with portions of cineritious matter in a
manner that I am not permitted to suppose you prepared
to comprehend, for I am not addressing you as anato-
mists.

688. Passing under a thick mass of medullary matter
(fig. 57, k,) which is one of the commissures of the

290 COLUMNS OF riBRES IN THE BRAIN.

brain (671), the fibres are again divided into four great
columns, one of which passes into each hemisphere of
the cerebrum, and one into each hemisphere of the
cerebellum.

689. From this point the fibres of the several columns
spread themselves out so as to run towards all parts of
the circumference of the brain, to terminate in the
cineritious matter of the convolutions.

690. But the mass of the brain vastly exceeds that
of the medulla oblongata, and most of its bulk is made
up of medullary matter, and consequently, of nervous
fibres. A very small proportion of these fibres are in-
terested in forming the commissures, which run trans-
versely, and by far the larger portion correspond in
their direction with those diverorins^ from the four co-
lumns mentioned in the tw^o last paragraphs. Hence it
follows that, as the fibres of the columns separate, on
their way to the convolutions (689), a great multitude
of other fibres, proper to the brain itself, are added to
the number, and we have no reason to believe that these
fibres, which never leave the brain, have any immediate
relation with the external senses. Even the fibres of the
spinal marrow, after they actually enter the brain, ap-
pear to lose their power of awakening consciousness
when irritated; for the brain itself is entirely divested
of feeling: you inay cut it or crush it piecemeal, without
making pressure on the spinal marrow, and the patient
will utter no complaint.

691. It is a curious circumstance, that all the fibres
running towards the convolutions are so arranged that
those passing to opposite sides of the same convolution
do not intermingle, but a line of demarcation exists
between them ; and by taking oflf a portion of the upper
surface of the brain, you may spread out the convolu-
tions, so as to make the surface flat, without tearing a
fibre. When water collects very slowly in certain
cavities existing in the brain, provided the dropsy
occurs in infancy, before the bones of the head are
firml}^ united, the greater part of the upper surface may
be distended, so as to resemble a bladder formed of

QUESTION OF THE FUNCTIONS OF THE BRAIN. 291

cineritious matter externally, and medullary matter
within. Yet such is the power of the vital functions
in adapting the frame to accidental circumstances, that
a child so affected may not lose its intellect. The
fibres are lengthened, so as to accommodate themselves
to their new position. Instances have been known, in
which the bones of the cranium have become perfectly
ossified over such alterations of the brain, and the
patients have reached a mature age, or even middle
life, with a head of twice or thrice the natural size ; but
such persons generally become idiots. I saw a case of
the kind in the almshouse of Newport, Rhode Island, in
1838 : he is still living.

692. Now, as every nervous fibre is a distinct organ,
having its own appropriate function (290), it is evident
that there are many nervous organs within the brain
whose functions must be different from the functions of
those which are found externally to the cranium. The
founders of phrenology have essayed the discovery of
these functions, which is as legitimate a subject of re-
search as is any thing connected with the nervous system.
But as consciousness and will are not functions of the
nervous system, it would be in vain to attribute any form
of these faculties to the nerves of the brain ; and it is
probably by the neglect of this fact that the founders of
phrenology have involved themselves with so many of
the moralists of the day, and have drawn down upon
themselves the hostility of some whose talents would
have been better employed in correcting the error than
in combating those doctrines of the science which are
susceptible of proof.

693. Phrenology is a physiological, and not a meta-
physical science. But some of its advocates have taught
the doctrine, that those organs of the brain which they
conceive to be the organs of the moral sentiments are
motor powers, or that all our conduct resulting from the
promptings of these sentiments, is the inevitable conse-
quence of peculiarity of organization; thus depriving the
individual of all control, and, of course, of all responsi-
bility ; a doctrine that sinks us at once and inevitably

292 QUESTION OF THE FUNCTIONS OF THE BRAIN.

into the darkness of materialism and fatalism, and one
w hich is utterly at war with the real history of the ner-
vous system. The nerves, as we have seen, are mere
media of communication between one external thing
and another ; and to say that one medium of communi-
cation communicates with another, is reasoning in a
circle : it is saying that one post-office communicates
with another. There must be a messenger to transmit
the message and an officer to receive it; where the
nerves of organic life are alone concerned, the message
may be sent by the stomach and received by the heart,
but where consciousness is interested, there must be
some independent being to whom the intimation is con-
veyed ; for experiment proves that a nerve of feeling
cannot be conscious of feeling (647), neither is any
nerve of the brain, and it is not even contended that any
other organ can be the seat of consciousness. But that
which is conscious, also wills, and coupled with its will
comes free agency diud. accountability ; — modified, it may
be, but not destroyed, by the nature of the evidence fur-
nished by the senses. The doctrine I have been com-
bating belongs not legitimately to the science, but has
been unnecessarily engrafied upon it by some of its
advocates.

694. What, then, are the functions of the nerves of
the brain ? Let us examine. The brain is evidently a
part of the system of nerves of animal life. We must
therefore seek for nervous functions of animal life not
otherwise provided with proper instruments. But the
nervous functions of animal life are those of the senses,
and those which lead to the performance of voluntary
motion. Now we know that there are no organs of
voluntary motion within the cranium, and we can trace
the nerves that govern the operations of all those exter-
nal to the cranium. These are already provided with
their proper nerves ; and as the same reasoning already
employed in relation to consciousness and will, applies
with equal force to all the other mental faculties, there
remain no known functions to be investigated except
^hose of the senses.

QUESTION OF THE FUNCTIONS OF THE BRAIN. 293

695. What are the senses ? They are the functions
of those organs which arouse to the mind the knowledge
of the existence and relations of external things.

696. Are there any senses necessary to the know-
ledge of the relations of external things besides sight,
hearing, taste, smell, and tact or feeling? And if so,
what part of the frame performs these functions 1

697. Nothing is better known than that there are
many individuals who have most perfect organs of
vision, so far as we are able to ascertain — persons who
see objects with the utmost distinctness, yet have no
power to discriminate between one colour and another.
Is it not probable, then, that the discrimination of colour
depends upon a different sense from that of mere vision?
If so, we can seek for its organs no where but in the
brain, for every external nerve of sense is already ap-
propriated.

698. One child has more natural affection for its pa-
rents than another, and some are exceedingly deficient
in it. What is a parent? It is an external thing, — an
object for the observation of the senses of the child. It
has relations with the child which are also objects of
the senses. The object is one which resembles very
closely thousands of other individuals of the same spe-
cies bearing a close resemblance to it. Yet the attach-
ment is so very strong that the child will often cling to
the parent in face of neglect and cruelty, while it will
turn from the greatest kindness in a stranger. What
informs the mind of the child of the relations in which
it stands to this parent ? We frequently speak of it as
a keen sense or feeling of affection. If it be a sense, it
must have its appropriate nerves, and these nerves can
exist only in the brain ; for it is totally different from
every one of the external senses.

699. One man has so keen a perception of the ludi-
crous, that nothing that is humorous in the relation of
external things can escape him. He will laugh by the
hour at the accidental resemblance between the coun-
tenances of an old horse and the man who is driving
him, while another, with an equally vigorous mind, will

294 PHRENOLOGY NOT DEPENDENT ON CRANIOSCOPY.

gaze at him with astonishment, and read him a homily
on his folly. This evidently depends upon a peculiar
sense ; and its organs must be sought in the brain.

700. When one event follows another on all occa-
sions, we are apt to call the first the cause, and the
second the effect — but this is not always true. Day fol-
lows night, but day is not the cause of night. In our
little experiment with the marbles and the balls of dough
(514), the blow of the first marble is the cause of the
motion of the last ; and this I presume you would per-
ceive at once, even if you had never heard a single
word on the subject of elasticity ; yet there are men
whom no explanation would convince that it was not
the result of jugglery. This perception of the relation
between cause and eflfect appears to depend upon a
sense ; and its organs must likewise be contained in the
brain.

701. Now the phrenologists contend that they have dis-
covered the organs not only of these senses but of many
others in the brain, by observations on the form of the
head. Probably they are right in some instances and
wrong in others. You can judge the questions for your-
selves, when age and experience have fitted you to
examine the weight of evidence which they adduce in
support of their position. The object of these and the
following remarks, is simply to communicate some prin-
ciples that may assist you in the research, should you
ever undertake it.

702. The art of estimating the developement and
energy of the internal nerves of the brain by examining
the external form of the head, is called cranioscopy, and
the question of its useful application is altogether distinct
from that of the truth of the science of phrenology. The
latter may be correct in its fundamental principle, that
diflferent parts of the brain are the organs of different
senses, and yet the former may be extremely fallacious.
I shall presently notice some of the principal sources of
error.

703. Before speaking of the mode pursued by the
founders of phrenology in attempting to determine the
functions of the nerves within the brain, it is right to

ORIGIN OF CRANIOSCOPY. 295

mention a few facts in relation to this subject, which
you may depend upon as correct.

704. The external surface of the head agrees very
nearly with that of the skull. Except on the temples,
where two very large muscles of the lower jaw take
their rise, the integuments of the head are very evenly
spread over the surface of the bone, and an anatomist
finds very little difficulty in making the proper allow-
ances for all varieties of thickness.

705. The external form of the skull corresponds so
nearly in most places with that of the brain, that the one
may be judged with sufficient nicety by examining the
other. The thickness of the bones varies in different
individuals, but the amount of difference is so slight that
there is not one case in a thousand in which it would
be found to confuse our estimate very seriously. The
bones also vary in thickness in different parts of the
same head, but the only situation in which this differ-
ence is important as influencing our judgment, except,
perhaps, in some extremely rare cases, is at the lower
part of the frontal bone, where the frontal sinuses are
placed, and the value of this difficulty has been stated
at paragraph 402, to which you may refer.

706. The celebrated Dr. Gall, the founder of modern
phrenology, commenced his observations on this subject
at a very early age, while still at school, and continued
them through a very long life. He was assisted and
succeeded by his pupil, Dr. Spurzheim, to whom, more
than to any other one man, we are indebted for our
present knowledge of the anatomy of the brain. The
plan of observation was this : An individual of marked
peculiarity of talent, such, for instance, as great facility
in acquiring languages, was examined with great care,
and if any unusual developement of a particular portion
of the head was observed, it was noted as the probable
seat of the faculty ; for Gall well knew that in any indi-
vidual, the larger a muscle, a nerve, or any other organ
may be, the greater is its functional power, provided it
is in a healthy condition. Every person possessed of
the same peculiarity in a remarkable degree who came

296 ORIGIN OF CRANIOSCOPY.

within reach of these gentlemen, was then compared
with the first, and with all others. If all were found
to possess the same peculiarity of developement, the
probability of its being the seat of the faculty was con-
sidered as much increased ; but if some were found
wanting, an error was acknowledged, and they endea-
voured to find some other developement common to all
the cases, while they sought, in the characters of the
persons observed, for some other trait of remarkable
talent which should explain the previously discovered
enlargement. After years of labour, they succeeded in
locating to their satisfaction a number of the organs of
the internal senses, or, as they have been pleased to call
them, the mental faculties. It would be difficult to num-
ber the multitude of examinations made by these gentle-
men in every corner of Europe. You are probably
aware that Dr. Spurzheim died in the attempt to con-
tinue the same research on this side of the Atlantic.
Their more careful and philosophical disciples have
enormously increased the amount of observation on this
interesting subject, and similar researches have been
extended by the friends and foes of the doctrine through-
out the whole range of the vertebrated animals. It is
now acknowledged, even by many who oppose the doc-
trine, that these investigations have reflected brilHant
light upon metaphysics, and have furnished us with a
comprehensive terminology of the human faculties.

707. The brain is nourished and developed on the
same principles with all the other organs. In common
with them it is actually enlarged as well as increased in
functional power by exercise, and the bones of the cra-
nium change their shape to accommodate the change,
even after the individual has arrived at mature age. In
advanced life it becomes smaller, like all other parts,
and the skull then either contracts upon it or becomes
thicker, in order to fill up the intervening space. Per-
sons ignorant of physiology have urged it as an objec-
tion to the attempt to judge what part of the brain has
been developed by measuring the form of the cranium
nn its upper surface, that the growth may have taken

SOURCES OF ERROR IN CRANIOSCOPY. 297

place at the base of the brain, and that the arch of the
cranium may be raised in consequence of its contents
being thrust up bodily : but this objection is without
foundation. It is a law of the animal economy, that
when the healthy growth of any organ in a cavity re-
quires a developement of its walls, they are enlarged to
accommodate the increased size of that organ, just where
the accommodation is most necessary, and without dis-
placing other important parts. Even the progress of
disease often shews this beautiful arrangement still more
remarkably: for most morbid anatomists have observed
soft tumors upon the dura mater within the head, which,
instead of pressing down upon the soft brain beneath,,
have risen up until they have appeared externally, the
hard bone being absorbed before them to give them
passage.

708. Whatever may be said or thought of the value
of cranioscopy as a guide in judging of the balance of
the different faculties in the head of an individual, and
of the light it throws upon education in pointing out
what organs of the brain are weak and require strength-
ening by trained exercise, there can be no doubt that
the difficulties opposing the comparison of the powers of
one individual with those of another are so great that
its apphcation with such a view is often as fallacious as
it is invidious.

709. On the principle that the larger an organ is, the
greater is its power, the phrenologists tell us that, other
things being equal, he who has the largest brain will
possess the greatest degree of mental power. But no-
thing can be more erroneous than this position, as it is
commonly understood ; for A. may have a much larger
head than B., yet from a certain disproportion between
the lobes of his brain, A. may be scarcely capable of
making himself an available citizen, while B. may pos-
sess a very energetic character. A man who should
possess enormous intellectual powers with scarcely any
passions, might be less dangerous to society, but he
could hardly be more useful to himself than a mail with
violent passions and verv little intellect. But, even grant=

298 TEMPERAMENT.

ing their position — in calculating the equality of other
things, the phrenologists take little notice of any thing
else than the temperament. They grant that a man
with a small head and a nervous temperament may be
more powerful than another whose head is large but
whose temperament is lymphatic. At the close of the
next chapter, which speaks of the temperaments, you
will find a notice of a most important and not uncom-
mon error upon this subject.

CHAPTER XVI.

OF TEMPERAMENT AND IDIOSYNCRASY.

710. In another part of this volume (270,271) it was
stated that the powers of life were unequally distributed
throughout the different systems of organs composing
the animal frame ; but each system and each organ
received such an amount of the vital powers as its
wants, with the energy and rapidity of its functions,
require. This produces an equilibrium of action through-
out the frame which is consistent with the highest
health.

711. But certain moderate changes in this balance
are observed to take place in different portions of the
human family without being absolutely destructive of
health. Circumstances of climate, education, heredi-
tary peculiarity, or habits of living, may produce a
change in the relative developement of any organ or
system of organs; thus giving unusual influence to those
portions of the frame in the general balance of life,
without inducing positive disease. And these changes
may be either general over a whole system, or local, in
a single organ.

712. The circumstances in which the individual is
placed may even require such changes, in order that

TEMPERAMENT. 299

health may be preserved; for the organization best
adapted to a cold climate is well known to be danger-
ous in a warm one. It is probably owing to the extent
to which the balance of life is capable of modification,
that man is indebted for his remarkable power of
becoming accustomed to variations of cHmate which
prove destructive to all animals, even to those of a
domestic character. Though these animals share large-
ly in the susceptibiHty of change, none of them, unless
it may be the domestic dog, will live beyond a cer-
tain range of latitude. We cannot transfer the camel
to Lapland, or the reindeer to the tropics: and you
will readily perceive, in the operations of this law, and
the effects of hereditary tendencies, the causes of most
of the pecuharities of nations and races of men as well
as individuals.

713. When an individual has all parts of his frame
so tempered to each other as to be balanced in the man-
ner most consistent with the health, longevity, and per-
fection of vital power, he is said to be of a natural
or correct temperament — if otherwise, he has a peculiar
temperament.

714. It is evident that the number of temperaments,
general or local, observable among mankind, must be
indefinite, but that the former are likely to be much
less numerous than the latter. When the word tem-
perament is used by physiologists without a prefix, re-
ference is made to the general modifications only. (711.)

715. Numerous as are the distinctions between races
and nations, we find, in all countries, a large number of
persons distinguished by the characters of a very few
general temperaments. The shades, the degrees, and
the intermixture of these in individuals are beyond
number, but in a very large proportion of mankind
some traces of one or more of them may be detected.

716. These general modifications of structure are
necessarily productive of peculiarities in the appearance
and in all the vital operations — in the effects of food and
medicines, and in the display of the mental faculties.
They are well worthy of such notice as we have space

300 TEMPERAMENT.

to giv^e them. Physiologists now generally enumerate
four principal temperaments : the sanguine^ the bilious,
the lymphatic or 'phlegmatic^ and the nervous. When
intermingled with each other, they are designated by
the titles sanguineo-iiervous, hi/io-nervous, &c.

717. The sanguine temperament, when moderately
marked, is considered as approaching most nearly to
the natural condition of health. It is the result of a just
balance between all parts of the vascular system, and
the other systems generally. When decidedly marked,
it produces a highly florid complexion, with a well-
rounded outline of all parts of the frame ; a moderate
degree of fulness, with the divisions between the mus-
cles well, but not strongly defined, so as to render them
decidedly, though not strikingly prominent; a skin
flexible, but not very yielding ; and the flesh firm but
compressible and elastic. The blood is highly coloured,
and tinges the cheeks, lips, gums, &c. of a brilliant red:
its serum and coagulable portions are equally balanced.
The animal heat is pleasant, moderate, and diffuses
itself readily. The perspiration is free but not exces-
sive. The colour of the hair and eyes varies from so
many accidental circumstances, that it is not a safe
guide in judging of general temperaments ; but, in the
sanguine, it is generally light, though rarely very light,
and very seldom black.

781. As you would naturally suppose, all the vital
operations and the mental faculties are carried on very
rapidly, and with full energy, in persons of this tempera-
ment. The nutrition of all parts is remarkably perfect:
the muscles are powerful, the mind vigorous, and the
feelings and passions quick.

719. When this temperament is excessive, the indivi-
dual becomes peculiarly liable to inflammatory diseases,
which are always sudden in their attack, generally
short in their duration, and violent. They often require
prompt and energetic depletion, but will rarely endure
well the long continuance of debilitating treatment.
The temper of such persons is also violent but evan-
escent. They pursue their studies and other mental

TEMPERAMENT. 301

exercises by paroxysms very energetically, but soon
weary of their occupations ; are speculativ^e, daring,
often incautious, and accomplish great results occasion-
ally, but rarely succeed in those pursuits that require
great prudence or untiring perseverance.

720. Sometimes the venous system is more developed
than the arterial, giving rise to a less general tempera-
ment, marked by a bluish or yellowish tint of those parts
of the surface which in the purely sanguine, are florid.
Persons of this temperament have veins unnaturally
large and liable to disease in advanced life.

721. Sometimes, the veins of the abdomen belonging
to the portal system (599), are, alone, thus unduly de-
veloped. When strongly marked, this is hardly con-
sistent with continued health, and very greatly modifies
the character of febrile and other diseases attacking
those in which it is displayed. I mention these two last
varieties merely as illustrations of partial or local tem-
peraments.

722. The bilious temperament is marked by an excess
of nutrition in the more solid parts of the body, and
especially in the fibrous organs. By some it is con-
sidered as indicative of the still greater energy of the
circulation ; be this as it may, there is an obvious
difference in the character of the blood in this tempera-
ment. Its coagulable portion is increased and its
serum is not so abundant. The lymphatic system is
less developed, and the fluids of the body bear a smaller
proportion to the solids than in any other temperament.
Very little fat is deposited. The person looks dry and
thin ; presenting angular and harsh outlines. The
veins are very prominent on the surface. The muscles
start out boldly, and are divided by deep depressions,
even in the face, giving a strongly marked character to
the countenance. The skin is dry and tightly drawn ;
the flesh hard, and the animal heat great, or even burn-
ing. The density of the blood seems to deepen the
colour of the hair and eyes, which are dark, and often
black. The complexion is usually swarthy.

723. Men of the bilious temperament have firmer, more

30a TEMPERAMENT.

energetic, and therefore less excitable nerves than those
of the former class. But all the vital operations, though
somewhat slow, are performed with great power and
certainty. Mentally and physically, they are capable
of long continued and untiring exertion. Their pas-
sions and their affections partake of this character.
They are fond of schemes demanding much time for
their accomplishment ; and pursue their object, whether
in love, hate, science, war, or business, with the long
trot of the wolf

724. TJie lymphatic or phlegmatic temperament is cha-
racterized by the superabundance of the cellular tissue
and serous fluids of the body, and is generally attributed
to an excessive influence of the lymphatic system. This
evidently marks an inferior degree of organization — a
general deficiency of developement — and it is the reverse
condition to that remarked in the bilious temperament.
The person is soft and disposed to be flabby ; there is a
great absence of tone ; the surface is pale, moist, and
cool; the hair and eyes are very light; the countenance
unexpressive ; and the temper imperturbable, in cases
which are very strongly marked. It is hardly necessary
to state that those who have this temperament naturally
and very completely matured, are peculiarly averse to
mental and bodily exertion. The blood has a supera-
bundance of serum, and the frame is not supplied with
proper nourishment ; and of course, the nervous sus-
ceptibility cannot be considerable.

725. The nervous temperament has been added to the
list in modern times, and its most peculiar characteristic
appears to be a peculiar liveliness of nervous susceptibi-
lity without a corresponding energy of the muscular con-
tractility. This condition is the reverse of that found in
the athletic, (which might be erected into a muscular
temperament,) and is common to those of sedentary or
luxurious habits. It is perhaps more frequently acquired
than inherited or constitutional. The nervous fibres in
this temperament are not unduly developed ; for this
would give them firmness and render them less suscepti-
ble. When acquired^ the nervous excitability is probably

TEMPERAMEPTT. 303

due to an increased flow of blood towards the nerves,
in consequence of their frequent and unnatural stimula-
tion. This condition is sometimes induced by studies of
too intense a character, or too long continued, and also
by sensual indulgence. It is not an uncommon infliction
upon the poet, the scholar, and the dissipated, and may
be either a cause or a consequence of their indulgences.

726. The nervous temperament is consistent with
great mental effort, particularly in the higher walks of
literature and the forum. When constitutional, it is
m.ore than probable that the nerves are really weaker,
or less thoroughly nourished than they should be ; for
debility of this kind is well known to superinduce in-
creased susceptibility. It acts like a magnifying glass
upon both the ills and the pleasures of life, and rarely
proves a blessing.

727. A temperament partaking of the nervous, but
also marked by an excess of the cellular tissue in a
vigorous condition, and not in the feeble state presented
in the phlegmatic temperament, is natural to children
and women. The same nervous susceptibility with the
rapidity of judgment and the evanescence of impres-
sions dependent upon it, as well as the same soft condition
of the nervous fibre, mentioned in the last paragraph — is
also proper to childhood and to the female sex.

728. Now these several temperaments being capable
of change by local circumstances, may be corrected by
judicious education and habits when they are produc-
tive of evil by their excess. Should I ever address you
upon the subject of Hygiene, or the art of preserving
health, there will be much to be said upon this subject,
but at present, it is sufficient to introduce two illus-
trations.

729. The proper use of muscular exercise, carried to

that extent which will give full developement to the |

muscles, will often correct a nervous temperament into [

a nervo-bilious or nervo-sanguine one, to the great ad- j;

vantage of the individual; and the bilious or sanguine |'
may sink by idleness and mental inactivity into the
phlegmatic, to his great disgrace.

304 TEMPERAMENT.

730. Now, as the principal general temperaments
depend upon the peculiar condition of some one system
of organs or tissues, either the vascular, the lymphatic,
the nervous, or the cellular; as portions of all these
systems enter into the construction of most organs ; and,
as an excess of either of them in any one organ must
constitute a peculiar local temperament ; it follows that
the greater part of the frame may display all the signs
of one temperament, while some individual organ, — the
brain, for instance, — may exhibit another.

731. But the brain is not subject to our observation.
We cannot tell what is its local temperament by cra-
nioscopy; and our only guide is the observation of the
conduct of the person as compared with his general
temperament. This fact seems to have been overlooked
by the phrenologists when they have undertaken to esti-
mate the relative capacities of different men, by the
total bulk of the brain.

732. A peculiar local temperament of a single organ,
often leads not only to a general alteration of the balance
of life, but also to strange and unusual tastes, which
cannot be disregarded with impunity. An idiosyncrasy
is defined to be a peculiarity of constitution which causes
a remedy or any other agent to act upon a particular
individual, as it would not do upon the generality of men.
Thus, some people faint at the smell of a rose, and eating
bitter almonds or crabs affects others with a nettle rash.
Now, although many idiosyncrasies may result from
other causes, many others certainly do form peculiar
temperaments of some one or more organs. We should
be cautious, then, in blaming others for an obstinate ad-
herence to certain apparently whimsical habits of diet
or other singularities in their mode of life.

733. And now, having completed this outline of some
of the chief principles of physiology, I bid my young
readers adieu, in the hope that it will prove a useful
guide to them in the studies and duties of future life.

QUESTIONS FOR PUPILS.

CHAPTER I.

Is motion a proof of life 1 Give some instances of motion in par.
inanimate things, 2

Is rest a proof of the absence of life 1 What is an eye-stone 1 3
Is growth a sign of life 1 Give instances of grovi^th in things

that have not life, 4, 5, 6, 7

Give instances of minerals appearing to grow like plants,. . . 8, 9
Are motion and growth sufficient of themselves to distinguish

things that have not life, from living things ? 10

Are birth and death distinctive properties of living things 1 . . 11
What is the first step in Physiology ] What is Physiology 1 11
Explain the differences between the motions of living things
and those of things that are not alive. Can the latter ever
move by their own efforts'? Give examples of motion in
inanimate things, and the causes that produce them. What
is said of the fall of a stone, the vibration of a spring, the

clicking of a watch, the crawling of an eye-stone 1 13

Are living things moved by external agents 1 Give examples, 14
Give proofs of motion in living things from a power within
themselves. Why do vegetables, when sprouting, direct
their shoots toward the light, and their roots toward the

nearest moist earth 1 15

Give further proofs from the effect of light upon the leaves and
flowers of plants. What is there curious in the history of

the plant called Venus's fly-trap "? 16

Do animals, as well as plants, display this internal power 1 . . 17
Is this power of regulating their own actions possessed hy any

thing that has not life 1 18

Why is an apparatus or machine necessary to all living things'?
What is an organ ? Give some examples of organs in living

things, 19

Why are animate things called organized beings ? 20

Whence do organized beings derive the matter of which they
are formed ? What is meant by the organization of such
beings 1... 21

26 ^305^

306 QUESTIONS FOR PUPILS.

What is organic matter? and what is inorganic matter? 22

What are organic remains ? and what are petrifactions ? 23

What is meant by the term system, as applied to organization?

Give some examples of systems, 24

Is it proper to apply the term system to the body 1 25

Explain the manner of growth as observed in organic bodies.
Do inorganic bodies ever grow by adding particles to their
interior, or by changing their nature so as to appropriate

them to their own use 1 27

Explain the manner of growth as observed in organized beings.
Do either plants or animals grow by adding matter to their
exterior] How are the bark of trees and the cuticle of ani-
mals replaced as they wear away 1 28-29

How are trees nourished 1 and how is man ] 30

Give some proofs that plants and animals can convert other

things into their own nature, 31

Give some proof that plants and animals possess the power of

moving their fluids from place to place within their frame, 32
Explain the difference between the mode of growth of a plant,
and the seeming growth of a sponge when placed in water, 33-34

Explain the seeming growth of metals when heated, 35

Can we explain what is life ] Does death produce any instan-
taneous change in the organization 1 36-37

CHAPTER n.

What proof is there that each of the different parts of an
organized being is possessed of its own peculiar mode of
life "? What is meant by the vital powers ? 38

What is meant by the term function? What by the term
vital functions ? 39

Can the different parts of an organized being preserve their
life in all cases, when separated from the body 1 Is the
integrity of all the parts generally necessary to the health
of the whole 1 40

Give some proof that the sound condition of certain parts is
indispensable to life in complex organized beings, while
certain other parts can be removed with impunity, or even
with seeming advantage to health,.-. 41

Why do small wounds often occasion the death of a plant or
animal 1 Give some examples. Why are not such wounds
always fatal 1 42

Give instances of the retention of life for some time, or perma-
nently, by parts cut off from the body of an animal. What
are you told of the earth-worm 1 43

What is said of the vitality of the tail of the snake 1 — the hind
legs of bull-frogs 1 — the head of the snapping turtle 1 — the
tortoise, and the shark 1 44-45

QUESTIONS rOR PUPILS. 307

What relation exists between the simplicity of organization

and the retention of life in separated parts ] Why is the

health of the whole body less dependent on the health of

the parts in the simple animals 1 46

Are the fluid parts of animals organized 1 — What is meant by

assimilation ? 47, 48

Does the simplicity of the blood or sap appear to correspond

with the simplicity of the organized being in which it is

found ] Does sap ever contain globules 1 49

Are there any plants containing substances resembling animal

matter ] 50

Is the blood of the simpler animals like to that of the more

complex] 51-54-55

What is said of the fluids of the medusa ? 52

What is said of the structu re and motions of the med usa ] 53

What reason can you now give for the preservation of life in

parts cut off from the simple animals 1 56

What is said of the structure of the hydra, its stomach, its

arms, and the motion of its food during digestion ? 57

What is meant by digestion 1 and by what means does the

hydra appear to digest its food % 58

How is the frame of the hydra nourished 1 59-60

What consequences follow when a hydra is turned inside out,

like the finger of a glove ? and what do they prove 1 61

What is said of the extent to which a hydra may be divided,

naturally or artificially, without destroying its life] 62-64

What is said of the organization of the hydra ? 65

What is meant by the terms cellular membrane and cellular

tissue] 66-67

Is cellular tissue found in all animals 1 — What is its structure

as seen under the microscope? — What is its appearance

when seen beneath the skin of animals ] 68

Give some proofs that the cells of this tissue communicate

with each other, from the mode of preparing animals for the

market, and from the history of wounds of the lungs, 67-68

What is the structure and appearance of fat] — What name is

given to the membrane that contains fat, by most writers 1 71

Does the skin of the hydra differ from cellular tissue ] 72

How does this animal digest, absorb, and breathe ] 73-74

How does the hydra preserve its form, and how does it perform

its motions ] 75

Has it volition] Give some proofs, 76-77

Is there much resemblance between the simplest vegetables

and the simplest animals ] 78

CHAPTER III.

Why are the simplest animals necessarily small ] < . . . . 79

Why are they seldom found except in the water ] SO

308 QUESTIONS FOR PUPILS.

To what class of animaiS does the zoanlhus belong 1 — What

is the name of the arms by which polypi take their prey ].. 81
What are cilia] — What their uses] and why do polypi g^ene-

rally require them 1 81-83

How are the cilia arrang« d in the flustra 1 83

How are they arranged in the vorticellal 84.

Is the motion of cilia like that of muscles in the larger ani-
mals ] Give a reason for your opinion, 85

Are cilia seen in animals much more complex than the polypi ]
Give an example. Are the cilia designed principally for

taking food in the more complex animals 1 86

Are any thing like cilia found in vegetables 1 Give an example.

Describe the cause of circulation in the chara-hispida, 87

In what respects do polypi resemble plants'? What name is
given to their buds 1 How do the gemmules move from
place to place 1 How do they choose their permanent resi-
dence 1 Is the motion of their cilia voluntary 1 88

Can many polypi, living in communities, enjoy common lifel 89
How do these communities construct their habitations? De-
scribe the form of the support of the community in sertu-
laria, in tubipora, in red coral and gorgonia, in madrepores.

How are coral rocks formed 1 89-94

What is meant by the term secretion 1 Give examples, from
polypi, from man, from shell-fish, reptiles, and the higher

orders of animals. What is meant by ossification? 94—98

What is nutrition 1 99

Give examples of fluid secretions and their uses, 100

What is meant by the term functions of organic life? and

what by the term functions of animal life 7 101

By what power is the blood driven from place to place, in order

to nourish the frame of animals ? 102

Is contractility a function of organic life? 163

Give examples of contractility in plants and animals, 104

Describe the physalia, and its contractility, 105-109

What is the cau^;e of the pain felt on touching the physalia? 107

Is vital contractility dependent on the will ? 110-111

What parts of animal bodies display contractility ? Ill

Does contractility display itself without excitement? Give
examples of its being excited by the will, and by other

agents, 112

What is meant by a stimulant? 113

What is meant by tonicity? What is tune? Give examples
from the history of palsy, and sleep. Give examples of

tonicity of the skin, and of the vessels, in fainting, 116-118

Is there more than one kind of contractility ? 119

CHAPTER IV.

Why is the stomach ramified in many medusae, and how 1 121-123

QUESTIONS FOR PUPILS. 309

What is meant by mastication, and masticatory apparatus 1 . . 124
Do you find teeth and jaws among the lower orders of animals 1 125
Aretha masticatory organs always seated near the mouth 1

What is said of the lobster ? and of shell-fish 1 126

What is the alimentary canal 1 127

What name is given to masticatory organs attached to the

alimentary canal 1 128

In what classes of animals are gizzards generally found 1 How

do fowls supply the want of teeth 1 129

In what animals is the alimentary canal more simple, and in
what animals more complex ] Give a reason for the differ-
ence, and examples from shell-fish, from fishes and birds,
from beasts that chew the cud, and from the camel,. . . .130-132

CHAPTER V.

Why is a muscular system necessary in the economy of ani-
mals of complex organization 1 133

Give an example of the great force with which muscles may
contract 1 133

Is the strength of a muscle dependent upon its vitality 1 133

Has the alimentary canal any muscles connected with it ] and
if so, for what purpose 1 134

How do the occasional contractions of muscles, when put in
motion, differ from the constant contraction of almost all
parts of the body, called tone 1 134

Why do some muscles act under the government of the will,
and others involuntarily 1 135-136

To what class of functions do the involuntary muscles con-
tribute? and why are they called muscles of organic life 1 .. . 137

Why are certain muscles called muscles of animal lifel 137

What is meant by the mixed muscles "? 138

What is a fascia 1 Where are fasciae found 1 139

Are the various fasciae separate or connected together? 140

What are the principal uses of fasciae, and how are they com-
posed 1 141-142

What would be the appearance of the fascia if all other parts
of the body were removed, and they alone were left ? 142

What is flesh 1 What is a muscle ] What constitutes the
muscular system ? 143

How are muscles generally attached ? By what are they
enveloped and surrounded ] 144—145

What is said of the structure of muscles'? of their colour in
different animals, and of the cause of cramp 1 Is every
fibre of a muscle a distinct organ? 146—147

What is said to be the appearance of muscular fibre under the

microscope 1 148

26^

310 QUESTIONS FOR PUPILS.

What part does the cellular tissue play in the construction of
a muscle 1 149

What change takes place in a muscle when it happens to be
caught between the broken extremities of a fractured bonel 150

Why do muscles generally require solid attachments in order
to move the body 1 What is said of muscular attachments
to the skin, and of the motions of the common snail 1 Do
the fascias ever furnish attachments to muscular fibres]. ... 151

What is said of the muscular motion of the snail 1 151

What is said of the formation of the shells of shell-fish, and
their muscular motions'? 152

What is said of the muscular motions of the echinodermata 1 153-154

How are the voluntary muscles attached in the Crustacea and
insects 1 155-156

What parts of the more perfect animals resemble the external
skeletons of the testacea, Crustacea, echinodermata, and in-
sects 1 156

Why would external skeletons be inconvenient to the higher
classes of animals 1 157

What great classes of animals are provided with internal ske-
letons 1 What name is given to the system of solid organs
composing the internal skeleton 1 157

How are the muscles attached in animals that have an osseous
system] Is any thing like true bone found in the inferior
animals 1 158

What is the condition of bone in very early life 1 What proof
is given of the softness of the bones in children? What
kind of matter is afterwards deposited in theml Of what
substances are the bones of the shark and many other fishes
composed ? 159

What substance is added to give hardness to the bones of the
most perfect animals'? 160

What effect is produced upon perfect bone by burning it or
boiling it a long time '? 161

What by soaking in an acid "? 163

Can bone be reduced to cellular tissue by art] 163

Can it be so reduced by disease ] Give instances, 164

What is the general importance of the cellular tissue in all
the special organs of animals'? and especially in young ani-
mals ] 165-166

When wounds are received, what part is it that unites first] 167

Why does cellular tissue form bone in one part of the body,
muscle in another, &c.] 168

What are the articular cartilages and their uses ] Give an
example of the articular cartilages, 169-171

What are the synovial membranes, their use and attach-
ments ] 172

What is synovia, and its use ] 172

What are the ligaments and their uses ] 173

QUESTIONS rOR PUPILS. 311

Describe a ligament and its structure, 174

What is the principal function of ligaments 1 174

Give an illustration. What happens to ligaments when joints

are put out of place or dislocated 1 174

What is the periosteum 1 175

What is the periosteum of the articular cartilages called] and

what name is given to the periosteum of the outer side of

the skull ? 176

Name the classes of organs belonging or appended to the

osseous system, 177

What is the appearance, structure, and use of tendon ? 178-179

Can tendons contract like muscles 1 Describe the mechanical

arrangement of tendons, and particularly that of an oblique

muscle of the eye, 180

Describe the character of the involuntary muscles, and the

action of the muscular coat of the stomach, 181

CHAPTER VI.

What are the blood-vessels ? What do they contain, and why
are they necessary in animals of complex organization] . . . 182

What blood-vessels are called veins ? 183

How do the valves of the veins effect the course of the blood 1 184
What is the form of the common centre toward which the
blood in the veins flows, in insects and worms 1 What is
its character, and what is it called in the higher orders of

animals 1 185

What are the arteries ? and what is their use 1 186

How are the arteries distributed 1 186

Explain the necessity of a connexion between the arteries and

veins, 187

Describe the capillary blood-vessels, 187

What is the circulation 1 188

W"hat are you told of the gradual additions of systems of
organs as animals rise in the scale of nature 1 Has the

earth-worm a circulation ] 189

What kind of circulation have insects "? 190

What is said of the circulation in the leech and the oyster?. . 191
How does nourishment find its way into the circulation of the

simplest animals that have a circulation 1 192-193

What is meant by the term chyme ? 193

Is the assimilation of chyme complete when it first enters the

body from the alimentary canal ] 194

What is chyme called after it has been imbibed or absorbed

into the body ] 194

Is chyle precisely similar to the blood, when it first mingles
with that fluid] '. 194

312 QUESTIONS FOR PUPILS.

How does the chyle reach the blood in the higher orders of
animals? Are the lacteuh a component part of the circula-
tory apparatus 1 .... , 1 95

What is the colour of chyle ] Is it organized ] 196

What is the mode of origin and tiie route of the lacteals?
Where and how do they empty their contents 1 197

What prevents the chyle from flowing the wrong way in the
lacteals ? 198

What is the structure of a lymphatic gland 1 199

Why cannot pieces cut from most animals continue to live
independently ? 200

Is there any other route by which substances reach the circu-
lation in the higher orders of animals, besides the lacteals 1
Give proofs, 201

Is there any reason to believe that cellular tissue and the
veins preserve their power of absorbing things in the higher
orders of animals, as they appear to do in the lower orders ? 203

What are the lymphaiics? and what is lymph ] 203

In what direction does the lymph flow] What is the course
of the lymphatics 1 and where do they empty their contents 1 203

Give a proof, from the history of poisoned wounds, that the
lymphatics do actually convey substances into the circula-
tion, 204

Are lymphatics found in the lower orders of animals? What
is meant by the absorbent system? What by the absorbents? 206

CHAPTER VII.

Why does a young animal require proportionally more food
than an adult 1 208

Why does an adult require any food at all ? 208-211

Can the wearing away of the skin and its appendages account
for this want ] 208

What \s perspiration? Give examples from plants and from
animals. Why do we not see liquid perspiration on the
surface of all animals at all times ? By what means can
you make it obvious at any time? What is insensible per-
spiration ? 209

Give some proof that a process analogous to perspiration is
going on at all times in the cavities of the animal body,. . . 210

Is the quantity of perspiration considerable? From what
fluid is it formed ? By what means is this constant loss of
substance compensated ? 211

Mention some other secretions that continually exhaust the
blood, and make food necessary to the adult, 212

Why are sick persons often able to go long without food ? . . . 213

In the history of the effects of starvation, what is the most

QUESTIONS FOR PUPILS. 313

obvious cause of death when animals are totally deprived of
food 1 213-315

What effects in addition to the exhaustion of fluids follow par-
tial starvation] and are these effects seen in persons labour-
ing- under fever 1 215

Can a man be virtually starved by disease, though still able to
take food and plentifully supplied with it ] Give a case, 215

By what route are solid portions of the frame carried out of
the body ] What is meant by the assertion that a starving
animal lives upon itself] 216

Does the same kind of constant absorption of solid parts ob-
served during disease or starvation continue during health
and plenty ] 217

Why are not the organs of an animal constantly rendered
smaller by absorption ] Why do the organs of a young ani-
mal constantly increase in size ] 218

Are any of the particles that compose an animal body perma-
nent during life ] What will be the condition of your bodies
in a few years] 218

What purposes are answered by the secretions in purifying the
blood ] ^ ^ 219

Name some of the secretions that assist in purifying the
blood, 220

Why do the blood-vessels secrete different fluids in different
places] 221

What points of general resemblance are found in the different
secreting organs ] Give examples, 222

What name is given to the special secreting organs ] 223

How are the blood-vessels arranged in the secretory glands ] 224

What are the form and function of the secretory ducts] 225

Can we trace any direct connexion between the capillaries and
the ducts of secretory glands] What is meant by transpi-
ration ] Does transpiration prove a functional resemblance
between the human cellular tissue and that which seems to
form the entire body of many of the inferior animals ] 226

Are the secretions ever rendered useful for special purposes in
the animal economy, other than the purification of the
blood ] Give proofs from the history of the tears, the saliva,
and the bile, 227

What is respiration ? Do plants respire ] 228

What is the principal object of respiration in animals ] 229

What are the principal ingredients of animal matter] 230

How are the surplus oxygen, hydrogen, and nitrogen of the
blood removed from the body ] 231

How is the surplus carbon of the blood chiefly removed, and
what is the chief function of the respiratory a'pparatus ?. . . . 232

Describe the process by which the respiratory organs separate
the carbon from the blood, and the result of that process,.. . 333

Do fish and other aquatic animals breathe water ] 234

314 QUESTIONS FOR PUPILS.

Can animals live in pure oxygen 1 Can air contain too much
oxygen to be heallhtul 1 235

Is actual contact between the atmospheric air and blood neces-
sary for respiration 1 236

By what means is the function of respiration performed in the
simplest animals 1 What is said of the toad in this respect ] 237

Does man breathe by his skin? What has this to do with
cleanliness 1 238

Describe the general plan on which the special respiratory
organs of those animals that have such an apparatus, are
formed, 239

What is the arrangement of the respiratory capillaries 1 How
are the respiratory organs generally situated 1 240

What organs in insects are called iracheas? and what is meant
by tracheal respiraiio7i ? 241

What is the general plan of organization in the respiratory
apparatus of aquatic animals'? What is their construction
in fishes? 242

What term is given to the aquatic breathing organs? What
is branchial respiration ? 243

How do the branchia act in accomplishing respiration? 244

Describe the hranchia of the common fresh-water mussel, and
the agency of the cilia in respiration, 245

What name is given to the respiratory organs of animals that
live in air ? What is meant by pulmonary respiration?. . . 246

Describe the pulmonary cavities and breathing organs of the
Lymnaea, and its mode of breathing, 247

Describe the arrangement of its respiratory capillaries,. . .247-248

Describe the construction of the respiratory cavities of the
larger animals, their air-cells, and capillaries. State the
position of the right and left lungs, 249

Describe the arrangement of the canal or duct that admits air
to the lungs, from the back part of the mouth to the air-cells, 250

What canal is called trachea in the larger animals? What
are the bronchia ? What are the bronchial tubes ? 251

If we compare the lungs to a secretory gland, what appendages
of the glands would correspond with the air passages ?
What lines these canals? What do they contain ? How
are they kept open ? 252

What part do the ribs and certain muscles play in pulmonary
respiration? What is inspiration? and what is expiration? 253

What additional part in respiration is played by the bones of
birds? 254

What change in the mode of respiration takes place as a tad-
pole is changed into a frog ? 255

Does all the blood of the inferior orders of animals pass through
their respiratory organs? Describe the mode in which the
blood passes to these organs in such animals, 256

QUESTIONS FOR PUPILS. 315

What effect has the imperfect respiration of inferior animals
on their vital functions "? , 257

Does all the blood of the superior orders of animals pass through
their lungs 1 What is the effect on their vital functions'? 258

What are the nutritive arteries of the respiratory organs, and
why are they necessary 1 259

How do the two sets of veins belonging to the lungs or bran-
chiae dispose of their blood 1 259

Are the terms branchial vessels^ respiratory vessels, and pul-
monary vessels applie.^ to the nutritive vessels 1 259

By what terra is the system of vessels that nourish the body
distinguished from the respiratory system 1 260

Describe the manner in which the human heart and that of
most of the larger animals is divided into four cavities. Is
the division between the right and left sides of the heart
complete or incomplete 1 261

Is the division between the two cavities on the left side com-
plete or incomplete ? Where do you find valves between
the cavities of the heart"? Wiiat is the structure of the
valves 1 What their attachments 1 261

What names are given to the four cavities of the heart ? 262

From what vessels do the auricles receive their blood 1 How
do they dispose of it ? 262

What vessels have their origin from the ventricles 1 262

What happens to the valves of the heart when the ventricles
contract? Are the arteries provided with valves'? Why
does not the blood flow back into the veins instead of passing
into the ventricles when the auricles contract "? 262

What is the name of the great venous trunk coming from the
head and upper extremities'? What kind of blood does it
contain "? What vessel brings back to the heart the blood
from the body and lower extremities'? Are these vessels
united into one 1 How do they communicate with the heart '? 263

Describe the entire route of the circulation, beginning at the
right ventricle and following the course of the blood till it
reaches the same cavity again, 264

What kind of blood is found in the right side of the heart, and
in all the arteries and veins leading to and frtDm it '? What
kind of blood is found in the left side and its vessels 1 How
is the heart itself nourished '? 265

Can the. heart be regarded as more than one organ '? 266

Why are the left auricle and right ventricle called pulmonary ?
Why are the right auricle and left ventricle often called
systematic ? 267

Is there such a thing as a double circulation '? What parts con-
stitute the respiratory or pulmonary circulatory apparatus ?
what the general or nutritive circulatory apparatus ?....... 267

Explain how the supply of blood is maintained in any part of
the body when any of its principal blood-vessels are totally

316 QUESTIONS FOR PUPILS.

obstructed by disease or accident. "What is the meaning of
anastomosis ] 268

"What danger results from tying a very large artery] What
happens when all the arteries or all the veins of a part are
obstructed 1 268-269

What class of organs contain most capillaries'? At what age
are the capillaries largest and most numerous 1 270

"Why do the young require more food, (proportionally,) than
older persons 1 270

Why does muscular exercise render the muscles larger and
stronger] Why docs it make the heart beat more rapidly 1
Does employment produce the same effect on other organs 1
Why does exercise hasten the breathing 1 271

What is the condition of the capillaries in muscles while em-
ployed ] 272

What is the effect of permanent rest on muscles 1 Give ex-
amples, 273

Do the same rules hold good in relation to the paramount rest
of other organs ] Why does something like fever come on
after dinner? What effect does thinking produce on the
capillaries of the brain? What moral and hygienic deduc-
tions are drawn from the facts stated in relation to employ-
ment and rest 1 274

Can any organ endure constant exercise ? Explain how the
heart obtains rest, 275

Illustrate the necessity of rest by the history of the effects of
travelling on nutrition in man and horse, 276

Explain the effects of sleep on nutrition. Those of late sup-
pers. What bad effects may follow, bodily and mentally,
from loss of sleep? At what age is most sleep required?
and why ? 277

Explain the effects of different degrees of over-exertion on the
nutrition and functions of organs. Give examples, 278

Explain the effect of over-exertion with deficient sleep, rest,
and food on the young in certain conditions of society,. . . . 279

What have the organs themselves to do wi*h completing the
process of nutrition ? , 280

CHAPTER VIII.

Why is a common mean of communication necessary between
the different organs of organic life? What system supplies
this necessity ? 281

In what animals do we first detect any thing like nerves?
What are the first signs or rudiments of a nervous system
observed among the simpler animals? In what classes of
animals is the nervous system studied to the best advan-
tasre ? 282

QUESTIONS FOR PUPILS. 317

Describe the appearance and give tiie names of the two kinds
of matter principally composinof the nervous system, 283

What is the composition of the brain, and the arrangement of
its two nervous ingredients 1 284

"What is the condition of the cellular membrane in the brain 1 285

What is the consistence of nervous matter in the brain ? How
is it protected from injury 1 286

What are the ganglia ? 287

Are there nervous filaments in the brain and ganglia] Are
the brain and ganglia called nerves 1 What are they called ?
How are the nerves connected with them? What is the
special function of the nervous centres ? 288

What is a nerve ] What kind of covering is given to a nerve
by the cellular tissue] How are the nervous filaments
covered ] 289

Is a nerve a single or a complex organ 1 290

Is each primary nervous trunk endowed with more than one
function ] Oive illustrations of the different functions of
different primary nerves,. 291

How are compound nervous cords formed ? What effect has
their complexity on their functions 1 Are the functions of
the filaments of compound nerves affected by this com-
plexity ] 292

Give an account of the origin and junction of nerves of feeling
and voluntary motion, with the eflfects of dividing the pri-
mary trunks or the secondary trunks of one of those nerves, 292

Describe what is meant by a plexus, and its effect upon the
functions of the nerves that result from it, 293

Describe bow a ganglion appears to be connected with its
nerves. Does a ganglion add any thing to a nerve 1 294

What appears to be the condition of nervous filaments when
they pass through ganglia ] 295

What effect has a ganglion on the functions of the filaments
of the nerves connected with it ] 296

How would you prove that blood-vessels and absorbents form
a part of every animal organ of which we kn-iv- the struc-
ture ] 297

Are the functions of animal organs dependent on their blood-
vessels 1 298

Are the functions of animal organs dependent on the nerves ]
Give proofs, 299

How is the nervous system divided into minor systems, and
what are they called ] 300

Describe the location and g^eneral arrangement of the nervous
system of organic life, 301

Are the organs supplied by the nerves of organic life and
those nerves themselves arranged regularly in correspond-
ing pairs] :. 301-302

318 QUESTIONS FOR PUPILS.

What is the general arranorement of the nervous system of
animal life, and the organs supplied by if? 303

Describe the general arrangement and connexions of the sym-
paiheiic nerve of those animals that have an internal
skeleton, 304

Describe what degree of connexion exists between the ner-
vous system of organic life, and the will and sense of feel-
ing in an animal, 305

Describe the mode in which the nerves of organic life influ-
ence those of animal life in sickness, 306

Give instances of the mutual influence of the two grand divi-
sions of the nervous system, as displayed in accidents, in
distentions of the stomach, and in intestinal irritations,. . . . 307

What name do we give to the cause of these associated phy-
siological actions ] and what do we know about this cause? 308

Describe the immediate effects of an impression upon a gan-
glionic nerve. Describe the secondary eff'ects when more
than one ganglion, or the whole nervous system of organic
life is interested. Describe the general effects when the
nervous system of animal life is involved in the impression, 309

Give proofs of the influence of strong impressions on the brain,
producing serious effects on the nervous system of organic
life, and the organs under its control, 310

Give proofs of the mutual dependence of the nerves and the
blood-vessels on each other, 311

What moral conclusions can you draw from the unity of the
human frame, which inculcate the importance of the study
of physiology, 312

Is there any proper brain in the animals that have no bony
skeleton 1 Whence are their nerves of special senses de-
rived 1 What is it that physiologists generally mean when
they speak of their brain 1 313

Have we solid ground for asserting the existence of nervous
matter in the most simple animals 1 314

W'ith what system of nerves in man can you compare the sim-
plest forms of the nervous system in the lower orders of ani-
mals 1 Which set of functions, — the organic or the animal, —
are brought to high perfection at the earlier stage in the pro-
gress of animal developement ] 315

Are the simplest animals possessed of senses, instinct, and
volition? What inference can you draw from the facts just
mentioned, as to the probable functions of the seemingly
simple nervous systems of the lower orders of animals that
have no internal skeleton, 315

What say you can be the origin of the obvious functions of
animal life, in beings that present no signs of nervous mat-
ter whatever? , . . , 315

What is said on the possibility of comparing the nervous sys-
tems of animals that have no bony skeleton, with those of

QUESTIONS FOR PUPILS. 319

animals that have such an apparatus, with a view to throw

light on the functions of the brain in man ■? 316

What is said of the propriety of the term scale or chain of
nature^ so often employed by writers, and used for conve-
nience even in this volume ? -. 317

CHAPTER IX.

What are the principal regions into which the body is di-
vided % 319-320

Describe the bounds of the part of the head which contains the
brain. What do you understand to be the meaning of the

word cranium ? 321

What part of the head is called the face] Does it include the

forehead ] 322

How do anatomists use the term neck 1 323

How is the trunk divided \ Describe the boundaries of the

chest and the abdomen, 324

What part of the trunk is called the pelvis "? 325

What are the principal contents of the chest 1 326

What are the principal contents of the abdomen ] 327

What do you understand by the terms shoulder, and shoulder-
joint "? 328

What do anatomists understand as the arm] and what is

called the forearm ] 329

What is said of the fundamental structure of the whole body? 330
What is said of the manner in which the organs are formed ] 332
What is said of the complex structure of the human skinT. . . 335
What names are given to the outer layer of the skin? Is it

organized 1 Has it any feeling 1 336

Is the cuticle of uniform thickness % 337

What is said of the resemblance of the nails and other cuta-
neous appendages to the cuticle 1 337-338

What is the origin and early condition of cuticle ? 339

Has the cuticle any pores I What causes its irregularity of

surface 1 340

What are the follicles of the skin called? What their struc-
ture] What their function] 341-342

What relation has the cuticle to the follicles ] 343

Where is the origin and what the mode of growth of the

hairs ] 344-345

What are the connections of the hairs w4th the cuticle] 346

What remarks are made on the colour of the hair ] 347

What are the functions of the cuticle ] Are they active or

passive] 348

What kind of a membrane lies next below the cuticle], ;. . . . 349
What is meant by the term papillae of the skin] What is the
name given to the middle membrane of the skin ] What

320 QUESTIONS rOR PUPILS.

is said of i!^e cause of differences of complexion in indivi-
duals ] 350

What is said of the influence of climate and exposure upon
the hues of races of men 1 351

What parts, other than the rete mucosum, are tinged with the
same colouring; matter? What proofs are there of the in-
fluence of climate and the seasons on the colour of quadru-
peds, fishes and birds 1 352

What is the name of the inner layer of the skin? What is the
papillary body ? 353

Of what is the true skin composed ? Describe the manner of
its organization, 354

What is the arrangement of the nervous matter and the nerves
on the outer surface of the true skin? W^hat is the function
of the papillre ? What is the common cause of the severity
of the pain in inflammations of the true skin? What causes
the commencement of mortification in carbuncle? 355

What are the situation, structure and function of the bulbs of
the hairs ? 356

What are the principal functions of the true skin? What are
the causes and nature of goose-flesh ? What is the condi-
tion of the sensibility of the skin in goose-flesh ? 357

What is the name given to the muscular coat of the skin found
in many animals? What is its structure? What its func-
tion ? What example is drawn from the history of the ele-
phant ? 358

What has the mtiscular coat to do with the motion of the hair
and feathers in quadrupeds and birds ? 359

Has the skin in man any muscular coat? 360

What do you understand by the term integuments ? 361

By what means are the different layers of the integuments
converted into one apparently simple envelope for the body ? 362

What are the connections of the integuments with the parts
beneath them ? Where are the connections most firm and
close ? 363

What is meant, in common language, by the term Jleshy, as
applied to personal appearance? Why do not the palms of
the hands, and the soles of the feet, become as fleshy as
other parts ? 364

What is said of the general formation of all the internal pas-
sages of the body ? 365

What happens to the external integuments when they approach
the mouth and nose ? What happens to the blood-vessels of
the true skin ? What to the cuticle ? What name is given
to the cuticle within the mouth and nose ? 366

W^hat chantje takes place in the function of the follicles, when
placed within the mouth ? Is there any radical difference
between the internal and external integuments ? 367

What part of the throat is called the pharynx? What is the

QUESTIONS FOR PUPILS. 321

arrangement of its muscular coat 1 What is the oesophagus "?
How is its muscular coat arranged 1 How does the oeso-
phagus terminate ] 368

"Where does the internal cuticle or epithelium of the alimen-
tary canal terminate 1 What is the extent of the mucous
membrane of the alimentary canal 1 369

What is said of the capillary blood-vessels of the mucous
coat 1 370

What are the villi 1 To what part of the external integuments
do they correspond 1 371

What is said of the mucous follicles and mucous glands?.. .. 372

What is said of the difference of the arrangement of the seve-
ral layers of the internal and the external integuments?. . . 373

What have the integuments to do with the ducts of the secre-
tory glands? What is said of the gall duct? What of the
integuments entering the air-passage ? What of the duct
conveying the tears to the nose ? 374

What is said of artificial or accidental ducts formed by the
integuments ? What is the nature of a fistula? Describe
the mode of curing a salivary fistula, 375

What circumstances may convert a portion of the internal
integuments into common skin, or a portion of the common
skin into mucous membrane ? 376

What is said of the causes and cure of excoriations in fat per-
sons and tTiose who neglect cleanliness, when the skin folds
upon itself and excludes the light and air ? 377

What resemblance is mentioned between the integuments of
man and the polypi and the hydra ? 378

Is there any deficiency of the integuments or passage through
them internally or externally ? 379

Why are the internal more liable to irritation than the external
integuments? Why are they less subject to pain? 380

What particular portions of the surface are most sensitive, and
why is sensation concentrated in them ? 380

What is said of the irritability of the orifice of the larynx?. . 381

What is the cause of suffocation in drowning and in poisonous
gases ? 382

What proof is there that the health of the lungs requires fre-
quent ablutions? Mention one of the causes of the good
effects of rubbing with the coarse towel, and wearing flannel, 383

CHAPTER X.

Why are the pieces of the skeleton more numerous in child-
hood ? 385

How many bones are there in the skeleton of an adult? On
what plan are they constructed ? Into w^hat great classes
are they divided ? What fills the cavities in their -sub-
stance ? 386

27*

322 QUESTIONS FOR PUPILS.

Describe the interior and exterior arrangement of the bones
in general terms, 387

What do you understand by the tables of the bones of the
cranium ] What name is given to the bony cellular struc-
ture between these tables'? Which of the tables is usually
the thicker] , 388

What is the arrangement of the walls of the long bones 1. . .. 389

What is the general arrangement of the bony matter within
the long bones'? What do you mean by the medullary
cavity of most long bones, and where do you find it *? 390

Is the medullary matter of bones formed anywhere but in the
medullary cavity '? 386-390

Describe the mechanical advantages derived from the peculiar
arrangement of the bony matter in the centre and at the
extremities of the long bones, 390

State the several names given by anatomists to the looser tex-
ture in the interior of the bones, 391

Why is it difficult to display the existence of cellular tissue in
the substance of bone ■? 392

How is the cellular tissue arranged in the cancellated struc-
ture ] 393

Are there any passages in the solid parts of bone'? Can you
see them 1 Describe their arrangement in the shafts of the
long bones and in the short bones, 394

W'hat effect does burning or long exposure produce on the
appearance of the bones? W^hat is the real internal struc-
ture of the solid portions of bone "? What occasions the
appearance of a tabular arrangement '? Is there any me-
dullary matter in the solid portions of bone? How can you
prove this '? 395

How do the blood-vessels find their way into the interior of the
bones ■? Where are they most numerous, and where most
rare? What classes of bones are supplied with one or
more large blood-vessels ? What are the distribution and
functions of those blood-vessels ? 396

Is bone possessed of the sense of feeling? Is the marrow? 397

Are the bones living organs? How do you know them to
be so ? 398

What is the cranium? How many bones compose it? Do
any of them assist informing the face? What is the
general form of the cranium ? Describe the general form
of its cavity and walls. How many great depressions are
there on its lower surface ? 399

What are the name, position, and general form of the anterior
bone of the cranium ? , 400

What are the frontal sinuses, and where are they formed ?
Describe their connexions and use ? 401

What is said of their character in childhood, and in women ?
What of their size, and relation to cranioscopy ? 402

QUESTIONS FOR PUPILS. 823

What occasions the staggers in sheep and deer 1 Does the
same accident ever happen to man ] 403

Describe the orbitar plates of the frontal bone, 404

What class of organs do the phrenologists locate behind the
frontal bone 1 405

Describe the parietal bones, their position, and principal con-
nexions, 406

What organs are located by the phrenologists under the pa-
rietal bones 1 407

Describe the occipital bone, its general form and structure.
Describe the form, position, and structure of its cuneiform
process, 408

Where is the great foramen of the occipital bone, and for what
is it designed 1 409

Describe the form and position of the occipital cross, 410

Describe the structure and important uses of the cross, 411

What portions of brain fill the four depressions divided by the
cross 1 412

Describe the position of the temporal bones. Describe the
squamous plate, 413

Where do we find the petrous portion of the temporal bone]
Name some of the important passages contained in it, . .414-415

What is the structure, and what the function of that large
prominence of the temporal bone felt just behind the ear 1 . . 416

How is the temporal bone connected with the bone of the
cheek? Where do you find the articulation of the lower
jaw-bone 1 417

What is said of the sphenoid bone, its position, and its cells 1 418

What is said of the position and structure of the ethmoid
bone 1 419

How are the bones of the cranium connected with each other"? 420

By what membranes is the cranium covered externally and
internally'? What is the condition of the bones of the
cranium in childhood ] How do certain savages flatten
their heads 1 What has this to do with cranioscopy ] 421

What is said of the process of ossification in the bones of the
head 1 422

What great advantages result from the imperfection of the
cranial bones in childhood ] 423-425

What changes take place in the form of the cranium from
mental exercise, and from age 1 426

Describe some of the mechanical advantages resulting from
the peculiar form of the cranium, 427

Describe the manner of the articulation of the head with the
atlas vertebra, and the motions of the joints, 423

What is the form and what the name of the uppermost ver-
tebra ] 429

What do you understand by the word condyle ? 430

324 QUESTIONS rOR PUPILS.

Describe the articulations of the head and atlas with the ver-
tebra dentata, 431-432

Describe the motions of these joints, 433-434

What preserves the upright position of the head ? 435

Whence does the head derive its muscles 1 436

How do rheumatism and palsy sometimes aflect the position of
the head, and why 1 436

Of how many bones is the face constructed 1 437

Describe tlie extent and structure of the upper jaw, 438

W^hat is said of the passage of nerves through the upper jaw,
and tic-douluureux ? 440

What is said in relation to the sympathetic connexions of the
nerves of the upper jaw % 441

Describe some of the peculiarities of the structure, mode of
growth and functions of the teeth. Have they sensation ?
What is the enamel 1 What is meant by the term alveolar
processes ] 442-445

What beconies of the socket when the tooth is lost"? 446

How are the infantile teeth throv.n off] What is there in the
history of horned animals resembling this ] 447

Wliat proof that an infant is not designed to be carnivorous do
you find in the history of the teeth ] 448-450

What proof is furnished by the teeth that a grown man was
not designed to live entirely on vegetables? 450-453

When should a child be allowed to commence eating freely of
the ordinary meats, according to the language of the teeth ] 451

What is the complete number of the infantile teeth, and how
are they classified ] 449-450-451

How many teeth replace the infant teeth, and how many teeth
has a man? 450-452

Wliy is inattention to the teeth injurious to the health] Why
are errors in diet injurious to the teeth ] 455

What is the spine ] Describe its general form, 457

What is the number of the vertebrae] How are they classi-
fied ] Describe the direction of curvature in the three prin-
cipal portions of the spine, 458

What occasions the conical form of the spine ] 459

Describe the general form of a cervical vertebra, and name
its several parts and processes. State which of the parts so
named are peculiar to the cervical, and which common to
all the vertebras except the atlas. Has the atlas any body] 460

Describe the articulations of the vertebrae with each other.
Of what substance are the intervertebral cartilages con-
structed ] 461

What is said of the effects of weight and age on these carti-
lages ] 463

In what manner are the spinal articulations strengthened by
ligamentous matter ] What is the spinal canal ] 463

QUESTIONS FOR PUPILS. 325

State some of the advantages resulting from having the spinal
column composed of many bones, 464

Describe the different degrees of mobility possessed by each
of the great portions of the spine, and why the dorsal por-
tion is nearly immoveable, 465

How is decay of the bodies of the vertebrae sometimes natu-
rally cured 1 Does age produce such changes 1 466

Describe some of the consequences resulting from the manner
in which the nerves pass from the spinal canal, 467

Describe the general form, position, and articulations of the
ribs. State what are their motions, 468

Describe the connexions, nature, and functions of their car-
tilages, 469

At what time of life are the cartilages of the ribs liable to
ossification 1 470

Describe the sternum and its position. With what bones and
cartilages is it articulated 1 What bony connexion has the
superior extremity with the trunk ] 471-472

"What muscles are the chief support of the chest to prevent
the ribs and sternum from sinking down by their own
weight 1 473

What part of the chest rises most in breathing] What is the
kind of motion performed by the sternum 1 What part of
the chest is most enlarged by the elevation of the ribs in
breathing, and why is it so 1 474

What consequences would you expect in relation to the mus-
cles of the breast and neck, from confining the lower ribs
by a ligature ? 475-476

State what is the agency of the muscles of the back of the
spine, in favouring the process of breathing, 478

Why is a habitual stoop injurious to respiration, and to the
nutrition of muscles and other organs 1 479

What bones form the pelvis'? 480-481-482

Give a general description of the sacrum. Is it a part of the
spine ] 480

Of what pieces is the os coccygis originally formed 1 Has it
any connexion with the spine ] 481

What and where are the ossa innominata? What have they
to do with the formation of the hip-joint 1 482

Name the bones upon which the shoulder is formed, 484

Describe the articulations and the functions of the clavicle,. . . 484

Illustrate the uses of the clavicle by a reference to animals
that are deprived of it, 485

Where is the spine of the scapula, and where does it termi-
nate] What bone is articulated with its extremity'? 486

Describe the form, position, and connexions of the process of
the scapula that assists in forming the shoulder-joint, 487

What is the extent of motion enjoyed by the arm, independently

326 QUESTIONS FOR PUPILS.

of the elbow 1 What accident is rendered more common by
this extent of motion 1 488

Describe the form of the upper and lower extremities of the
humerus, 487-488-489

On what bones is the forearm constructed 1 490

What is the general form of the ulna? Describe the manner
in which it articulates with the humerus at the elbow-joint, 491

What is the general form of the radius 1 Describe the manner
in which it articulates with the humerus and the ulna at
the elbow-joint, 492

Describe the prone and supine positions of the hand, and the
manner in which they are brought about by the motions of
the bones of the forearm, 493

How are the bones of the forearm connected with the joint of
the wrist 1 494

How many bones are there in the wrist 1 How are they
united ■? Wken taken collectively, what are they called?
What is their arrangement at the wrist joint? 495

Describe the form, position, and connexions of the metacarpal
bones. What is there peculiar in the motions of the meta-
carpal bone of the thumb 1 496

Describe the number and situation of the phalangeal bones,. . 497

What number of bones contribute to form the superior extre-
mity 1 Are there any bones connected with the tendons'?
If so, where do you find them, and w^hat is their function? 498

Describe the formation of the hip-joint, 500

Describe the position of the head and neck of the femur or os
femoris, 501

What effect has age on the head and neck of the os femoris 1
Mention some of the consequences, 502-503

What is the character of the internal structure of these parts'? 504

Describe the general direction and the form of the lower ex-
tremity of the OS femoris, 505

On how many bones is the leg constructed 1 What are their
names'? To which bones of the arm do they severally cor-
respond 1 506

Describe the formation of the knee-joint. Describe the form,
position, and use of the patella, 507

What is said of the ligaments of the knee-joint and their ac-
cidents ■? '. 508

What are the motions of the ankle-joint? What are the
tarsal bones ? How many of them are there ? What have
they to do with the motions of the foot ? 509

With what parts of the upper extremities do the tarsal bones
correspond ] 510

What bones of the lower extremities correspond with the
metacarpal and phalangeal bones of the hand ? 511

What is the whole number of bones in the lower extremities? 512

QUESTIONS FOR PUPILS. 327

To what extent do the ligaments contribute to the preservation

of the bones of the skeleton in their proper relative position'?

What other system of organs contributes to this duty 1 . . . . 513
State the disadvantages that would result from the elasticity

of the bones, were they solid throughout the whole skeleton, 514
State what parts of the skeleton are rendered inelastic for the

prevention of these evils, 515-518

In what manner does the spine contribute to this purposed. . . 516
How is the chest protected from the force of blows 1 517-518

CHAPTER XL

State the three fundamental postulates of the argument on
muscular equilibrium in chapter xi, 519-520-521

What renders most men right-handed ] Which is generally
the stronger leg 1 522

What exercises are mentioned as counteracting such changes
of form ] 523

How does natural left-handedness affect the figure? What
conclusion do you draw from these facts 1 524

Does the weakness of any set of muscles produce effects of a
character similar to those jnst mentioned 1 525

Describe at length the series of changes of figure resulting
from a club-foot on the right side, 525-526-527

Are these changes usually carried very far in cases of club-
foot ? 528

Describe at length the changes of form and position likely to
result from the attempt to sit up straight on seats without
backs 529-530-531

Describe the manner in which these changes are modified by
the usual attitude (facing the table) in reading and writ-
ing, 532-533

How are these vices of figure from bad attitude at the desk to
be prevented 1 534

W^hat is the common cause of a habitual stoop 1 535

Give the philosophy of the effects of Minerva braces, 536

How should a stoop be cured ] Give illustrations, 537

Describe the manner in which the eye adapts its focal distance
to the distance of the object, 538-539-540

What is the change in the eye in old age, and its cause"?
What is the most frequent cause of shortness of sight in
youth, and how may acquired short-sightedness be cured ] . . . 541

What is the immediate cause of squinting? What may pro-
duce the habit of squinting? How has squinting been
sometimes cured by a surgical operation 1 542

Is squinting generally a habit? What other cause often pro-
duces it ? 543

828 QUESTIONS FOR PUPILS.

"What are the principal effects of squinting upon the vision,
and on the organization of the eye ] 544

What produces inequality of the focal distances of the two
eyes 1 What is said of its relief and cure 1 545

What is said of the arrangement and tonicity of the involun-
tary muscular fibres of hollow organs 1 546

What is a sphincter 1 549

What is the name of the sphincter of the stomach 1 547

Describe the muscular equilibrium of action and reaction,
between the body of the stomach and the pylorus during
digestion, 547-548-549

What are the effects of the habitual over-distention of hollow
organs and their sphincters, as displayed in the stomach 1 550

In what respect do the effects of the over-stimulating quali-
ties of food or drink differ from those of their excessive
quantity ] 551

CHAPTER XII.

How are the intercostal spaces occupied 1 » 554

What is said of the muscles which draw the arm backwards 1 555
How are the fleshy walls strengthened on the anterior part of

the chest"? 556

What occupies the space between the uppermost dorsal verte-
bra, the two superior ribs, and the upper end of the sternum ? 557
What divides the cavity of the chest from that of the ab-
domen] 558-559-560

What is the general form and position of the diaphragm?. . . . 561
What are the principal contents of the chest 1 What is the

position of the heart? Which of the lungs is the larger 1 . . 562
Explain the general arrangement of the serous membranes,
and the particular arrangement of the serous membranes

of the chest, 563-568

Into how many serous chambers is the chest divided?. . . .565-566
Describe the mode in which the trachea divides to reach the

lungs, 567

What is said of the usefulness of the double serous division

between the two sides of the chest ? 568

How many cartilages contribute to form the larynx 1 Describe

their position and mention their names, 569-570-571

How is elocution subjected to the laws of gymnastics ? 571

Where is the hyoid bone found, and what are its connexions? 573
What is the use of the cords attached to the arytenoid carti-
lages ? What are they called? . 571

Describe the arrangement of the mucous membrane as it
passes from the trachea to the mouth and pharynx. What
IS meant bj'- getting a drop the wrong way ? 572-574

QUESTIONS rOR PUPILS. 329

What is the reason of the difficulty experienced in curing

inflammations of the larynx ] 574

Describe the form, position, and function of the epiglottis, 575-576
By what muscular arrangement are the walls of the abdomen

completed where the bony walls are deficient] Describe

the arrangement of these muscles, 577-578-579

"What is the name of the serous membrane of the abdomen,

and in what manner does it envelope the abdominal viscera 1 580
By what route do the blood-vessels and nerves find their way

to the viscera 1 581

Describe the difference between the mobility of different

viscera and its cause, 581-582-583

What peculiarity is observed in the arrangement of serous

membranes about organs subjected to great distention?. . . . 584
Are the abdominal viscera really included in the cavity of the

peritoneum ■? 585

Describe the relative position of the lungs, the diaphragm, and

the liver, 586-587

Where is the gall-bladder situated 1 588

Where is the spleen] What are its structure and function? 589

For what is the abdomen chiefly designed ] 590

How is the stomach connected with the oesophagus] What

names are given to the two extremities of the stomach]. . . 591
Describe the position of the stomach and its extremities,, . . . 592
Describe the position, direction, and function of the duodenum,

and its accessories, 593

Describe the connexions of the small intestines, 594

What process is carried on in the small intestines, and how

is the mucous coat modified to promote it ] 595

Describe the manner in which the small terminates in the

great intestine, 596

What is the ccecum ] What is the apendicula vermiformis] 597
Where is the ccECum situated ] Describe the different por-
tions of the colon as regards their route and connexions,. .. 598
Describe the character of the vena portae and the circulation

in the liver, with the origin of bile, 599

What connexions exist between the functions of the liver and

those of the lungs ] 600

Is the portal system of veins provided with valves ] 601

Mention some of the ill effects of pressure on the abdomen as

influencing the circulation of the blood, 602-603-604

CHAPTER Xm.

Describe the action of the intercostal muscles, and those of
the neck and back in effecting inspiration, 6Q5-608

Describe the agency of the diaphragm and the abdominal mus-
cles in inhalation, 609

330 QUESTIONS FOR PUPIL&,

Describe the process of exhalation, 610

"What consequences of the dependence of respiration on the
condition of the muscular system are particularly men-
tioned ] 611

What is said of the effects of age on the mechanism of breath-
ing? 612

Describe the effects of mechanical restraint of the muscular
motions of the chest and abdomen, 613-616

What is said of the effect of cleanliness on the health of the
lunors ] 617

CHAPTER XIV.

How is the secretion of saliva stimulated 1 619

How are some of the ill effects of chewing tobacco accounted
for? 620

What illustrations of the ill effects of bolting provisions at
meals are given? How may milk be rendered wholesome
for adults who cannot take it fresh 1 621

What is said of the action of the stomach on food and on the
general effects of debility of the abdominal muscles on
digestion ? 622

Describe the action of the stomach upon successive portions of
the food 623

What is said of the immediate effects of a meal on the circula-
tion, and the necessity of rest after it ? 624

What distinction is made between the absorption of meats
and drinks 1 625

What process is effected in the duodenum? What do you
understand by the peristaltic motion of the intestines?. . . . 626

Describe the process of vomiting, and its connexion with the
discharge of bile, 627

What membrane is essential to the formation of a blood-
vessel, and where is it found the only coat of a blood-vessel ? 630

What protects this membrane in places external to the bones? 631

Why is a third coat necessary in the arteries ? Describe its
structure and functions, 632-633

Describe at length the effects of exercise on the circulation in
the veins, 634-639

CHAPTER XV.

Is there any proof that any thing material passes along the
nerves when they exercise their functions ? 641

Tell what we know of the cause or effect of nervous action in
the nerves of organic life, 642

Wliat is stated in proof of the fact that every nervous fibre

QUESTIONS FOR PUPILS. 331

has its own peculiar function'? Prove that this function

resides in all parts of the fibre, 643-644

Can nerves communicate impressions one to another? 645

What nerves communicate with the mind'? Where do the

nerves of sense chiefly originate ■? 646

Have the nerves of the five senses really any consciousness of

sensation] What proof is given to the contrary '? 647

Describe the location, function, and general arrangement of the

dura mater, 648

Describe the falx and the tentorium, 649

What important parts are separated by the tentorium ■? 650

Describe the lesser falx, 651

Into how many compartments is the cavity of the cranium
divided by the falx and tentorium 1 Wiiat names are given
to the portions of the brain separated by these membranous

processes, 652

Describe the membrane lying immediately below the dura

mater, 653

What is said of the convolutions of the brain ] 654

Name and describe the membrane lying beneath the arachnoid, 655
Describe the various external divisions of the brain from the

text and the accompanying figure, 656-657-658

Recapitulate the general structure of the substance of ihe

brain, 659

What is said of the condition of nervous fibres within ganglia '? 660
What is said of the origin and termination of the fibres of the

brain ■? 661

What proof is there that the communication between the
mind and the nerves does not take place in the cortical
substance ■? What great deduction is drawn from this

facf? 662-663

What proof is there that consciousness and will are not func-
tions of any part of the brain ? 664-665

But if consciousness and will are not functions of the whole
brain or of any part of the brain, of what part of the organi-
zation are they functions "? 666

What is it that is conscious and wills '? 667

What proof is drawn from the history of disease to show that
our mental operations are modified by our organization?... 668

What is said of the seat of the mind 1 669

What is the real general nature of the brain viewed as com-
pared with other nervous organs '? 670

Are there any distinct nerves in the brain ] If so, by what

name are they generally called 1 671

In what order are the different parts of the brain developed as

we ascend from the inferior animals to man'? 672-673-674

In what way does the brain become developed in the advance

from infancy to manhood "? 675

Describe at length the proofs that are given of the fact that the

332 QUESTIONS FOR PUPILS.

mental faculties advance with the developement of tlie
brain, 676-679

What is said on the claims of phrenology f 680

What parts of the nervous system occupy the spinal canal] 681

What appearances are presented by a horizontal section of the
spinal marrow ] 682

What is the course of the four columns of the spinal marrow ] 683

What is added to the spinal marrow in the cervical portion of
the spinal canal 1 684

What is the real structure of the spinal marrow as compared
with other parts of the nervous system ? 685

Describe the manner in which the columns of fibres enter the
head , 686-687

Describe the manner in which the fibres distribute themselves
after enterincr the brain, 688-689

Do the fibres of the spinal marrow and medulla oblongata form
the bulk of the brain ] Has the brain any feeling ] 690

Describe the arrangement of the medullary fibres that admits
of the enlargement of the head in dropsy of the brain, 691

What is stated as one of ihe principal errors of most phreno-
logists in investigating the functions of the multitude of
organs forming the human brain 1 692-693

Is phrenology a physical or a metaphysical science? 693

In what class of functions should we seek for the functions of
the nervous fibres of the brain 1 694

What are the senses ] 695

Give some reason for supposing that man requires other senses
than those called the five senses to enable him to judge of
all the physical properties of matter; and state where these
organs can be found, 696-697

Give some reason for supposing that man requires peculiar
senses to awaken his instinctive feelings, and state where
Ave should seek their organs, 698

Give some reasons why man requires peculiar senses to awaken
his faculties for reasoning on cause and effect, resemblances,
the order of the time of events, and other things which
have nothing to do with the general physical properties of
matter, 699-700

What think you of the opinion of phrenologists on this
subject ] . . .' 701

What is the difference between phrenology and cranioscopy ?
May the principles of the one be true and the practice of
the"^other fallacious? 702

How does the surface of the head agree with the form of the
skuin 704

How nearly does the form of the skull agree with that of the
brain 1 705

State how Dr Gall endeavoured to investigate the functions
of the cerebral organs, 706

QUESTIONS FOR PUPILS. 333

Can the exercise of the faculties alter the form of the cranium'?
Why does not a developement of the base of the brain give
rise to an elevation of the top of the head 1 707

Is it as easy to compare the developement of the brain in two
individuals, as it is to determine the relative developements
of different parts of the brain in one individual 1 708

On phrenological principles is it true that the larger the head
the more powerful is the mind of the owner? 709

CHAPTER XVI.

"What do you understand by the term temperament? 710-713

Can the general balance of vital power between different

parts be altered consistently with health ] 711

Are such alterations of balance ever rendered necessary by

circumstances 1 712

What is meant by a natural or correct temperament ? 713

Is the number of temperaments limited 1 714

How many general temperaments are commonly acknow-
ledged by physiologists 1 715-716

Describe the s-anguine temperament, 717

What is the effect of the sanguine temperament on the mental

operations 1 718

What are the effects of an excess of the sanguine tempera-

inent? 719

What is said of undue predominance of the venous system?
What is said of the undue predominance of the portal sys-
tem ? 720-721

Describe the bilious temperament, 722

What is said of the mental and physical powers of endurance

in the bilious temperament ? 723

Describe the lymphatic or phlegmatic temperament, 724

What is said of the nervous temperament ? 725-726

What is said of the peculiar temperament of women and chil-
dren ? 727

Can a temperament be changed by treatment? Give ex-
amples 728-729

Can the frame have one temperament and a particular organ

another ? 730

What difficulty does this throw in the way of cranioscopy ?.. 731

What is said of the causes and nature of idiosyncrasy ? 732

28*

GLOSSARY

Of the terms used in this work, with derivation and accent :
as well as plural and genitive forms, when necessary ;
the words not yet adopted into English being printed in
Italics.

Abdo'men, n. Latin, from abdere, to cover or hide. 325,

Abdom'inal, adj. appertaining to the abdomen.

Acetah'ulum, n. PI. acetabulce. Latin, a vinegar cup. The
cavity of the hip joint. 500.

Ad'ipose, adj. Latin, adeps, fat. Appertaining to fat. 71.

Anastomo' sis, n. PI. anastomoses. Greek, the formation of a
mouth or opening. The junction of two vessels. 268.

Anten'na, n. PI. antenna. Latin, the yard of a ship. The feelers
of insects, crabs, spiders, &c. 19.

Aor'ta, n. Greek, oopr'*;. The great artery of the nutritive sys-
tem. 264.

Appendic'ula, n. Latin. A little appendage. 597.

Ary'tenoid, adj. Greek, apvtrj^, a ladle, and f tSoj, form ; ladle
shaped. A membrane of the brain. 571.

Au'ricle, n. s. Latin, auricula, the external ear. A receiving
cavity of the heart, so called because it has an appendage re-
sembling an ear. 262.

Bran'chia, n. PI. hranchicB. Latin, the gill of a fish. The organs
of breathing in aquatic animals. 243.

Bria'reus, n. Latin, a fabulous giant, with a hundred arms. A
genus of the order of sea-stars. 94.

Bron'chia, n. PI. bronchiae. Latin, the branches of the wind-
pipe. 252.

CanceVli, n. Latin, used only in the plural, cross-bars. The
meshes of a net-work of broad fibres. Imperfect cells. 391.

Can'cellated. Composed of cancelli.

Carbace'a, adj. Latin, from carbasus, a linen garment. 83.

CsiT^diac, adj. Greek; xapSta, the heart. Relating to the heart.
Lying towards the heart. 591.

Car'pus, n. PI. carpi. Latin, the wrist. 495.

Car'pal, adj. Appertaining to the wrist.

Ca'va, adj. PI. cavcR. Latin, feminine of cavus, hollow. 263.

(334)

GLOSSARY. 335

Cerehel'lum, n. PI. cerebella. Latin. The lesser or posterior

brain. 412.
Cere'brum, n. PI. cerebra. Latin. The greater or principal

brain. 412.
Ce'reus, n. PL cerei. Latin, a waxen taper. A genus of plants. 16.
Chafra, n. PL charce. Latin, the name of an unknown plant. The

name of a modern genus of aquatic plants. 87.
Chyle, n. Greek, xdXoj ; juice. The nutritive fluid in the frame

of animals. 194.
Chyme, n. Greek, xvjxos ; juice. The nutritive portions of food,

when prepared to enter the frame of animals. 194.
avium, n. PL cilia, an eye-lash. 82.
Cil'iary, adj. Appertaining to, or armed with cilia.
Cineri'tious, adj. Latin, cineritius, ash-coloured, or like to

ashes. 283.
Cm'cum. n. PL cceca. Latin, a deep cavity. 597.
Com'missure, n. Latin, commissura, a knot, or joint. A band of

fibres, or a firm joint connecting two similar organs together ;

as the two sides of the brain, or two bones of the cranium. 671.
Con'dyle, n. Greek, xov8v^o^, a knuckle. A prominent portion of

bone, forming part of a moveable joint. 430.
Cor'tical, adj. Latin, cortex, bark. Appertaining to or forming

the rind or bark. 284.
Coc'cyx, n. Genitive coccygis. PL coccyges. Latin ; a cookoo.

A bone resembling a cookoo's beak. 481.
Cranios'copy, n. Greek, x^aviov, the scull, and axoTi^v, to view.

The art of examining into the form of the brain by viewing the

head. 402.
Crib'riform, adj. Latin, from cribrum, a sieve. 419.
Cri'coid, adj. Greek, from xpcxoj, a ring, and ftSoj, form. Ring-
shaped. 570.
Crustac'ea, n. Latin, from crusta, a crust. A class of animals

covered with a crust or shell like that of the crab. 155.
Cu'neiform, adj. Latin, from cuneus, a wedge. Wedge-shaped. 408.
Cu'tis, n. Latin, the skin. The true or living skin, as distinguished

from the cuticle or scarf skin. 353.
Cyathe'na, v. Greek, xvaOsiov, a little cup. The name of a spe-
cies of animalcule, formed like a little cup. 84.
Degluti'tion, n. Latin, deglutio, the act of swallowing. 227.
Denta'ta, adj. Latin, toothed. Tooth-like. 431.
Di'aphragm, n. Greek, hcuppary^a, a partition. The muscle that

divides the abdomen from the thorax. 560.
Duode'num, rt. Latin, from duodeni, (counted) by twelves. The

first twelve fingers-breadth of the small intestine. 593.
Du'ra, adj. Latin, hard. 648.
Echi noder' mata, n. Greek, from rixtvo^, a hedge-hog, a sea-urchin,

and bepixa, a hide. A class of cold-blooded marine animals, with

a tough skin, generally armed with prickles. 152.
En'siform, adj. Latin, ensiformis, sword-shaped. 471.

336 GLOSSARY.

Epiglol'tis, n. Greek, from sxt, upon, and yXwr'T'tj, the mouth-piece
of a flute, or the opening of the wind-pipe. 575.

Epithe'lium, n. Greek, from £n;t, upon, and OrpM, to bloom. The
cuticle covering the red part of the lip, the mouth and oesopha-
gus. 366.

Eth'moid, adj. Greek, from jy^wo?, a seive, and ftSoj, form. A bone
of the skull and nose, so named from its cribriform plate. 419.

Falx, n. Genitive folds ; pi. falces. Latin, a sickle. A sickle-
shaped portion of a membrane of the brain. 649, 652.

Fascia, n. PL fascicB. Latin, a band or girdle. 138.

Fem'oral, adj. Appertaining or relating to the thigh, or thigh-
bone.

Fe^mrir, n. Genitive femoris ; pi. femora. Latin, the thigh; the
bone of the thigh, or os femoris.

Fib'ula, n. PI. fibulae. Latin, a brace or cramp. The smaller
bone of the leg. 506.

Fills' tra, n. Latin, a calm of the sea. A genus of polypi, which
build their cells chiefly in quiet water. 83.

Fora'men, n. PI. foramena. Latin, an aperture. 409.

Front's 1, adj. Latin, from frons, the forehead. Appertaining to
the forehead. 404.

Gan'glion, n. PI. ganglia. Latin ; from Greek yoyy^tor, a tumour
upon a tendon or nerve. Now, a nervous organ, in which the
fibres of various nerves are intermingled. 287.

Gem'mule, n. Latin, gemmulus^ or little gem. The living bud
separated from sponges and some polypi, which multiply the
race. 88.

Glot'tis, n. Genitive, glottidis. Latin; from the Greek yXo-r'T'tj,
the mouth-piece of a flute. The opening of the wind-pipe. 571.

Gorgo'nia, n. PI. gorgoneae. Latin, a tribe of corallines, branch-
ing like shrubbery, named from the fabulous Gorgons, whose
heads were armed with snaky locks. 93.

Gy'rans, part. Latin, gyrare, to whorl. Whorling round. The
specific name of a plant. 105.

Hedysa'rum, n. Greek ri^vsa^ov, a genus of pod-bearing plants ;
from T^St'f, sweet or pleasant. 105.

Hepat'ic, adj. Latin, hepaticus, from hepar, the liver, — appertain-
ing to the liver. 599.

His'pidus, adj. Feminine, hispida, neuter hispidum. Latin, hairy ;
thorny ; prickly, 599.

Hu'merus, n. s. Genitive, humeri. Latin, the shoulder ; the bone
of the arm. 487.

Hy'drogen, n. Greek, v5wp, water, and yfwow, to produce. A gas,
which, in burning, produces water. 230.

Hy'oid, adj. Greek, DOft5jj,from the letter v, and stSoj, form. Shaped
like an ypsilon. Applied to the bone which supports the base
of the tongue. 573.

Idiosyn'cracy, n. Greek, idto^, proper, ovv, together with, and
jfpacftf, the temper of tlie blood or humours. Mixed with the

GLOSSARY. 337

proper conformation of the blood. An individual peculiarity in
the constitutional balance of the vital structure which produces
health. 732.

Ima'go, n. Latin ; an image or picture. The perfect state of in-
sects ; especially of the butterfly and moth. 99, 100.

Imbibi'tion, n. Latin, from in, and bibere, to drink. The act of
sucking in. 192.

InnominaUus, adj. Feminine, innominata, neuter, innominatum.
Latin ; unnamed ; of little celebrity. 482.

Intercos'tal, adj. Latin, from inter, between, and casta, a rib.
Placed between the ribs. 304.

Lac'teal, n. Latin ; Lac, genitive lactis, milk. A vessel convey-
ing chyle; «(^>, appertaining to chyle (from the milky colour
of chyle). 195.

Lar'va, n. PI. larvae. Latin ; a mask. An insect in its first form
after leaving the egg; as, a caterpillar. 99, 100.

La'rynx, n. Greek, ^opvyl ; the upper portion of the wind-pipe, in
the throat. 569.

Lympha'tic, n. Latin, lympha, watery humour. A vessel convey-
ing towards the heart, the lymph, — a watery fluid ; adj., apper-
taining to the lymphatics.

Mad'repore, n. Latin, mador, moisture, and pora, a loose calca-
reous stone. A genus of corals. 94.

Ma'ter, n. Latin ; mother. 648.

Medu'sa, n. PI. medusae. Latin ; one of the fabulous Gorgons,
whose hair was turned to snakes, by Minerva. A genus of
gelatinous marine animals, with long stinging tentaculse, called
sea-nettles. 52.

Medul'la, n. Latin ; the marrow. This term is also applied to the
nervous matter contained in the spinal canal. 646.

Megalis'ta, adj. Greek, from fj.eya^, powerful, great. 105.

Metacar'pus, n. Greek, jxt-ta, next to, and xaprttcoi/, the wrist. The
five bones forming the palm of the hand. 496.

Metatar'sus, n. Greeki^ ftsra, next to, and i-apsoj, the heel. The
five bones forming the chief part of the instep. 511.

Mollus'cus, n. PI. mollusca. Latin, a nut with a thin shell. A
class of soft-bodied animals resembling and including those of
shell-fish. 152.

Muco'sus, adj. Feminine, mucosa, neuter, mucosum. Latin, mu-
cous. 350.

Mus'cipula, n. Latin, from musca, a fly, and capere, to catch. A
fly-trap. 16.

Neuralgia, n. Greek, vevpov, a nerve or tendon ; and yoooj, pain.
Pain of a nerve. 614.

Neurele'ma, n. Greek, vsvpov, a nerve or tendon, and XtjUjua, that
which is peeled off! The membrane investing a nerve. 289.

Ni'trogen, n. Greek, j^tt'pov, any salt used in washing, and yEwcuo,
to produce. A gas obtained from nitre or salt-petre, a salt which
was formerly used in washing. 50.
29

IHHI

338 GLOSSARY.

Oblonga'tus, adj. Feminine, oblongata ,• neuter, oblongatum. La-
tin, oblong, 646.

Occipital, adj. Latin, oc'ciput ; genitive, occipitalis; the back
part of the head. Belonging to the back part of the head. 408.

Oeso'phagus, n. Greek, oirso^, wicker or basket work, and (j)ayw, to
eat. The canal leading from the throat to the stomach; the
gullet. 368.

Os, n. s. PI. ossa. Latin ; a bone. 482.

Os'seous, a/Ij. Bony ; relating to, or composed of bone. 157.

Ossif'ic, adj. Latin, os, a bone, and facere, to make. Creating
or depositing bone.

Ossifica'tion, ji. The act of forming or depositing bone ; a conver-
sion of other living structures into bone.

Os'sify, V. To change into bone ; to form bone.

Ox'ygen, n. Greek, o|ff, an acid, and yswaco, to produce. A gas
composing part of air and water, which, uniting with other sub-
stances, produces many of the acids. 280.

Pan'creas, n. Greek, 7<au, all, and xpea^, flesh. A secretory gland
near the stomach, supplying the duodenum with a fluid resem-
bling saliva. 227,327.

Pancreat'ic, adj. Belonging to, or coming from the pancreas.

Pan'nicle, n. Latin, panniculus^ diminutive of pannus, a gar-
ment. 358.

Papilla, n. PL papillae. Latin ; a nipple. 350.

Pap'illary, adj. Composed of, or belonging to papillae.

Fatel'la, n. PI. patellae. Latin ; a pan. The bone forming the
cap of the knee. 507.

Paries, n. V\. parietes. Latin; a wall. The sides of a cavity.

Parie'tal, adj. Latin, from paries, a wall (or side of a building). 406.

Pel'vis, n. Pi. pelves. Latin ; a basin. The part of the skeleton
which gives attachment to the bones of the lower extremities. 325.

Perichondrium, n. Greek, Tispt, around, and xovSpo^, a cartilage.
The membrane investing a cartilage. 176.

Pericra'nium, n. PI, pericrania. Greek, tdpi, around, and xpawov,
the skull. The external periosteum of the skull, exclusive of
the face. 176.

Periosteum, n. Greek, rtjpt, around, and oatsov, bone. The mem-
brane enveloping bone. 175.

Peristal'tic, adj. Greek, from rcspi, upon, and oteMM, to contract or
press. Applied to the vermicular motion by which food is urged
along the alimentary canal. 697.

Peritone'um, n. Greek, rtspttomtoi/, the membrane stretched over
the contents of the abdomen. 580.

Pe'tal, n. Latin, petalum. The botanical name for the flower-
leaves of plants, 16,

Pe'trous, adj. Latin, from petra, a stone. Very hard ; stony. 414.

Phal'anx, n. PI phalanges. Latin ; a troop or body of soldiers
drawn up in close order. A term applied to each range of bones
between corresponding joints of the several fingers or toes. 497.

GLOSSARY. 339

Phalange'al, adj. Appertaining- to the phalanges.

Pha'rynx, n. Greek, fpapvy^, the upper part of the gullet 368.

Phe'nomenon, n. PL phenomena. Latin, from the Greek, ^aivofuvov,
an appearance in nature. 10.

Physa'lia, n. Greek, ^vaam, a bubble. A genus of gelatinous ani-
mals which float like bubbles on the ocean. 105.

Pi'a, n. Latin ; fern, of pius, tender, delicate. 655.

Pleu'ra, n. PI. pleurse. Greek, rtuvpa, the side ; the rib. The
membrane which is stretched over a lung, and which lines the
corresponding side of the thorax. .565.

Plex'us, n. Latin ; a piece of platting. A net- work of nerves. 293.

Pol'ypus, n. Greek, rio'KvTiovi, many-footed. A class of marine ani-
mals with many tentaculse, which construct the corals and coral-
lines. The term was formerly given to the cuttle-fish, and is
now vulgarly applied to the Hydrae, which are fresh-water ani-
malcules. 81.

Por'ta, n. Genitive, sin. portae, gen. pi. portarum. Latin ; a gate.
Thus: vena porta;, the vein of the gate; more frequently, vena
portarum, the vein of the gates : from the chief cleft or en-
trance into the liver, called the gate or gates of the liver. 599.

Pu'pa, n. PL pupae. Latin ; a doll. An insect in the inactive state,
during which it is changed from a larva to an imago. 99, 100.

Pylo'rus, n. Greek, ytuJuopoj, a watchman at the gate; a janitor.
The lower end of the stomach, where circular muscular fibres
stand guard against the passage of undigested matter. 547.

Ra'dius, n. V\. radii. Latin ; the spoke of a wheeL A line drawn
from any central point within a curve, or curved solid, to the
circumference or periphery. 492.

Red turn, n. PL recta. Latin ; from rectus, straight. The straight
intestine. 598.

Re'te, n. s. Latin ; a net. A net-work. 350.

Retic'ular, adj. Latin ; from rete, a net. Netted ; forming mesh-
es. 391.

Sa'crum, n. Latin ; the bone of the pelvis which forms the next
to the last portion of the spinal column, called the coccyx. 480.

Scapula, n. PL scapulae. Latin ; the shoulder-blade. 484.

Seba'ceous, adj. Latin," sebaceus, producing or relating to tal-
low. 341.

Secre'tory, adj. Latin, from secretus, put aside. Performing the
office of separating matter from the circulating fluid. 223.

Sertula'ria, n. Latin ; a diminutive ofsertum, a wreath. A genus
of polypi. 91.

Sig'noid, adj. Greek ; from the name of the letter j, sigma, and
ftSoj, form. Shaped like the letter s. 598.

Sphe'noid, adj. Greek, a^^vonSs?, wedge-shaped. 418.

Sphincter, n. s. Latin ; a bundle of muscular fibres, closing an
orifice by their contraction ; thus ; sphincter palpebrarum is an
anatomical name of the muscle which closes the eyelids. 549.

Squa'mous, adj. Latin, squam.eus, scaly. 413.

*^" GLOSSARY.

Ster^num, n. Latin ; the breast-bone. 468

Tarsus, n PI. tarsi. Latin; tlie heel. 'The back oart of th^

?:i^tr;rLa';!nr:i:nt-64'9"^"^ ^^^"^^^^^^^^- ^^''^^•

"^dltTf :;;ei!:fis^^ ilr ^"'^^^"^' ^°^'^^^^ ^^^^ ^ ^^^^1- The

™'ta,«. PL a;6i^. Latin; the shin-bone. 506.

I ho rax, n. Latin ; the chest. 197, 324.

Thora'cic. Belonging to the chest.

rrach'ea, n PI. trachea. Greek, ^pa=c..a, the wind-pine 251

Also applied to the air-passages in insect^. 241 ^ ^ *

iranspiration, 71. Latin, trans, beyond, and spirare to breathe

An exhalation through any membrane ' ^^^^t^^'

ri^6j>or'«, n. PI. tubipor^, Latin, /^^6^^,, a tube and mru. «

calcareous stone. A genus of polypi. 92 ^ ' ^

Ul na. n. Latin; the elbow; the fore-arm * The hnno ^f fi.« ^

arm which forms the principal part ofThe I^l^'nt III "'"
Vena, n. PL vense. A vein. 591. '' *

VeVa,ac?7. Latin ; feminine of verws, true. 353

XTe's :f a v^:;::' T9r ^ ^'^^"' ^'^^'^^-«' ^-- ^av-

''s{me:%5'7. ^'' '"''''" ^^^"' ^ J^^^' ^ bone of the
Fis^cusn PI. z,W«. Latin; an internal organ; as the brain

stomach, heart, &c. 580. ^ ' '

FortoZ7a, n PL t;or//c6fe. Latin; diminutive of vortex • a

whirling body. A genus of animalcules '

THE END.

Mil

CON

GBESS

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